Sexual intercourse
Overview
Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

 enters a female's vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

 for the purposes of sexual pleasure or reproduction. The entities may be of opposite sex
Sex
In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

es, or they may be hermaphroditic
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...

, as is the case with snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s. The term may also describe other sexual penetrative
Sexual penetration
Sexual penetration is a sexual activity that involves the entry into a bodily orifice, such as the vagina, anus or mouth, with a body part or an object....

 acts, such as anal sex
Anal sex
Anal sex is the sex act in which the penis is inserted into the anus of a sexual partner. The term can also include other sexual acts involving the anus, including pegging, anilingus , fingering, and object insertion.Common misconception describes anal sex as practiced almost exclusively by gay men...

, oral sex
Oral sex
Oral sex is sexual activity involving the stimulation of the genitalia of a sex partner by the use of the mouth, tongue, teeth or throat. Cunnilingus refers to oral sex performed on females while fellatio refer to oral sex performed on males. Anilingus refers to oral stimulation of a person's anus...

 and fingering
Fingering (sexual act)
Fingering is the manual manipulation of the clitoris, vulva, vagina, or anus for the purpose of sexual arousal and stimulation. It may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities. To "finger oneself" is to masturbate in this...

, which can be practiced by both heterosexual
Heterosexuality
Heterosexuality is romantic or sexual attraction or behavior between members of the opposite sex or gender. As a sexual orientation, heterosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, physical or romantic attractions to persons of the opposite sex";...

 and same-sex
Homosexuality
Homosexuality is romantic or sexual attraction or behavior between members of the same sex or gender. As a sexual orientation, homosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, or romantic attractions" primarily or exclusively to people of the same...

 partners.

Sexual intercourse typically plays a powerful role in human bonding
Human bonding
Human bonding is the process of development of a close, interpersonal relationship. It most commonly takes place between family members or friends, but can also develop among groups such as sporting teams and whenever people spend time together...

, often being used solely for pleasure and leading to stronger emotional bonds.
Encyclopedia
Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

 enters a female's vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

 for the purposes of sexual pleasure or reproduction. The entities may be of opposite sex
Sex
In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

es, or they may be hermaphroditic
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...

, as is the case with snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s. The term may also describe other sexual penetrative
Sexual penetration
Sexual penetration is a sexual activity that involves the entry into a bodily orifice, such as the vagina, anus or mouth, with a body part or an object....

 acts, such as anal sex
Anal sex
Anal sex is the sex act in which the penis is inserted into the anus of a sexual partner. The term can also include other sexual acts involving the anus, including pegging, anilingus , fingering, and object insertion.Common misconception describes anal sex as practiced almost exclusively by gay men...

, oral sex
Oral sex
Oral sex is sexual activity involving the stimulation of the genitalia of a sex partner by the use of the mouth, tongue, teeth or throat. Cunnilingus refers to oral sex performed on females while fellatio refer to oral sex performed on males. Anilingus refers to oral stimulation of a person's anus...

 and fingering
Fingering (sexual act)
Fingering is the manual manipulation of the clitoris, vulva, vagina, or anus for the purpose of sexual arousal and stimulation. It may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities. To "finger oneself" is to masturbate in this...

, which can be practiced by both heterosexual
Heterosexuality
Heterosexuality is romantic or sexual attraction or behavior between members of the opposite sex or gender. As a sexual orientation, heterosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, physical or romantic attractions to persons of the opposite sex";...

 and same-sex
Homosexuality
Homosexuality is romantic or sexual attraction or behavior between members of the same sex or gender. As a sexual orientation, homosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, or romantic attractions" primarily or exclusively to people of the same...

 partners.

Sexual intercourse typically plays a powerful role in human bonding
Human bonding
Human bonding is the process of development of a close, interpersonal relationship. It most commonly takes place between family members or friends, but can also develop among groups such as sporting teams and whenever people spend time together...

, often being used solely for pleasure and leading to stronger emotional bonds. Non-penetrative sex
Non-penetrative sex
Non-penetrative sex is sexual activity without vaginal, anal, or oral penetration, as opposed to the penetrative aspects of those activities...

 (for example, non-penetrative cunnilingus
Cunnilingus
Cunnilingus is an oral sex act performed on a female. It involves the use by a sex partner of the mouth, lips and tongue to stimulate the female's clitoris, vulva, or vagina...

) has been referred to as "outercourse", but may also be among the sexual acts contributing to human bonding and considered intercourse. The term sex can be taken to mean any mutual genital stimulation (i.e. all forms of intercourse and "outercourse"), and as with most forms of sexual interaction, individuals are at risk for contracting sexually transmitted disease
Sexually transmitted disease
Sexually transmitted disease , also known as a sexually transmitted infection or venereal disease , is an illness that has a significant probability of transmission between humans by means of human sexual behavior, including vaginal intercourse, oral sex, and anal sex...

s. Thus, safe sex
Safe sex
Safe sex is sexual activity engaged in by people who have taken precautions to protect themselves against sexually transmitted diseases such as AIDS. It is also referred to as safer sex or protected sex, while unsafe or unprotected sex is sexual activity engaged in without precautions...

 practices are advised.

Religious beliefs often play a role in societal views regarding sexual intercourse, other sexual acts, and their purpose. Some sections of Christianity
Christianity
Christianity is a monotheistic religion based on the life and teachings of Jesus as presented in canonical gospels and other New Testament writings...

 commonly view sex in marriage as holy and for the purpose of reproduction, while other sections do not. Modern Judaism
Judaism
Judaism ) is the "religion, philosophy, and way of life" of the Jewish people...

 and Islam
Islam
Islam . The most common are and .   : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...

 view sexual intercourse between husband and wife as a spiritual and edifying action. The limits of marriage
Marriage
Marriage is a social union or legal contract between people that creates kinship. It is an institution in which interpersonal relationships, usually intimate and sexual, are acknowledged in a variety of ways, depending on the culture or subculture in which it is found...

 and concubinage
Concubinage
Concubinage is the state of a woman or man in an ongoing, usually matrimonially oriented, relationship with somebody to whom they cannot be married, often because of a difference in social status or economic condition.-Concubinage:...

 within these traditions has changed over time, along with corresponding views of acceptable sexual behavior. The teachings of Hinduism
Hinduism
Hinduism is the predominant and indigenous religious tradition of the Indian Subcontinent. Hinduism is known to its followers as , amongst many other expressions...

 and Buddhism
Buddhism
Buddhism is a religion and philosophy encompassing a variety of traditions, beliefs and practices, largely based on teachings attributed to Siddhartha Gautama, commonly known as the Buddha . The Buddha lived and taught in the northeastern Indian subcontinent some time between the 6th and 4th...

 on sexuality have differing interpretations. Buddhism's injunction to "refrain from sexual misconduct" finds its interpretation and practical definitions at the level of the individual. However, within each of these major religious traditions exist subgroups with varying stances on acceptable sexual practices, and some religious groups prohibit monks and nuns from engaging in sexual intercourse altogether.

Sexual intercourse between non-human animals is more often referred to as copulation; for most, mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...

 and copulation occurs at the point of estrus
Estrous cycle
The estrous cycle comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. Estrous cycles start after puberty in sexually mature females and are interrupted by anestrous phases or pregnancies...

 (the most fertile period of time in the female's reproductive cycle), which increases the chances of successful impregnation
Internal fertilization
In mammals, internal fertilization is done through copulation, which involves the insertion of the penis into the vagina. Some other higher vertebrate animals reproduce internally, but their fertilization is cloacal.The union of spermatozoa of the parent organism. At some point, the growing egg or...

. However, bonobo
Bonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...

s, dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s, and chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

s are known to engage in sexual intercourse even when the female is not in estrus, and to engage in sex acts with same-sex partners. Like humans engaging in sex primarily for pleasure, this behavior in the above mentioned animals is also presumed to be for pleasure, and a contributing factor to strengthening their social bonds.

Bonding and affection

In animals, sexual intercourse ranges from a purely reproductive activity to one of emotional bonding between mated pairs. It typically plays a powerful role in human bonding
Human bonding
Human bonding is the process of development of a close, interpersonal relationship. It most commonly takes place between family members or friends, but can also develop among groups such as sporting teams and whenever people spend time together...

. In many societies, for example, it is normal for couples to have frequent intercourse while using birth control
Birth control
Birth control is an umbrella term for several techniques and methods used to prevent fertilization or to interrupt pregnancy at various stages. Birth control techniques and methods include contraception , contragestion and abortion...

, sharing pleasure and strengthening their emotional bond through sex even though they are deliberately avoiding pregnancy.

In humans and bonobo
Bonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...

s, the female undergoes relatively concealed ovulation
Concealed ovulation
Concealed ovulation or hidden estrus is the lack of distinctive signaling that the adult female of a species is "in heat". These signals may include swelling and redness of the genitalia in baboons and bonobos Pan paniscus, pheromone release in the feline family, etc...

 so that both male and female partners commonly do not know whether she is fertile at any given moment. One possible reason for this distinct biological feature may be formation of strong emotional bonds between sexual partners important for social interactions and, in the case of humans, long-term partnership rather than immediate sexual reproduction.

Humans, bonobos, dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s, and chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

s are all intelligent social animals, whose cooperative behavior proves far more successful than that of any individual alone. In these animals, the use of sex has evolved beyond reproduction, to apparently serve additional social functions. Sex reinforces intimate social bonds between individuals to form larger social structures. The resulting cooperation encourages collective tasks that promote the survival of each member of the group.

The concept of love belongs to the domain of the virtues and to higher cognitive function
Cognition
In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...

, and is thus generally reserved for humans. When applied to animals, "love" is used largely for its colloquial meaning. In certain contexts, such as scientific research into emotional bonding, "love" is given a neuroscientific or neurochemical
Neurochemical
A neurochemical is an organic molecule, such as serotonin, dopamine, or nerve growth factor, that participates in neural activity. The science of neurochemistry studies the functions of neurochemicals.-Prominent neurochemicals:...

 definition (rather than a human or a virtuous definition), and in such contexts human and animal intercourse are considered equivalent.

Reproduction and sexual practices

Vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

l sexual intercourse, also called coitus, is the human form of copulation. While its natural purpose and result is reproduction, it is often performed entirely for pleasure and/or as an expression of love and emotional intimacy. Coitus is the basic reproductive method of humans, and may be preceded by foreplay
Foreplay
In human sexual behavior, foreplay is a set of intimate psychological and physically intimate acts between two or more people meant to create desire for sexual activity and sexual arousal. Either or any of the sexual partners may initiate the foreplay, and they may not be the active partner during...

, which leads to sexual arousal
Sexual arousal
Sexual arousal, or sexual excitement, is the arousal of sexual desire, during or in anticipation of sexual activity. Things that precipitate human sexual arousal are called erotic stimuli, or colloquially known as turn-ons. There are many potential stimuli, both physical or mental, which can cause...

 of the partners, resulting in the erection
Erection
Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...

 of the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

 and natural lubrication
Vaginal lubrication
Vaginal lubrication is a lubricating fluid that is naturally produced in a woman's vagina. Vaginal lubrication or moistness is present at all times, but production increases significantly during a woman's sexual arousal in anticipation of sexual intercourse...

 of the vagina. To engage in coitus, the erect penis is inserted into the vagina and one or both of the partners move their hips to move the penis backward and forward inside the vagina to cause friction, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasm
Orgasm
Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...

 in either or both partners is achieved. For females, stimulation of the clitoris
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...

 plays a significant role in sexual intercourse; most achieve orgasm only through clitoral stimulation.

Penetration by the hardened, erect penis is additionally known as intromission, or by the Latin name immissio penis (Latin for "insertion of the penis"). During ejaculation, which usually accompanies male orgasm, a series of muscular contractions
Muscle contraction
Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same...

 delivers semen
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...

 containing male gametes known as sperm cells or spermatozoa from the penis into the vagina. The subsequent route of the sperm from the vault of the vagina is through the cervix
Cervix
The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall...

 and into the uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...

, and then into the fallopian tube
Fallopian tube
The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges are two very fine tubes lined with ciliated epithelia, leading from the ovaries of female mammals into the uterus, via the utero-tubal junction...

s. Millions of sperm are present in each ejaculation, to increase the chances of one fertilizing an egg or ovum
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...

 (see sperm competition
Sperm competition
Sperm competition is a term used to refer to the competitive process between spermatozoa of two different males to fertilize an egg of a lone female. Competition occurs whenever females engage in promiscuous mating to increase their chances in producing more viable offspring...

). When a fertile ovum from the female is present in the fallopian tubes, the male gamete joins with the ovum, resulting in fertilization
Fertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...

 and the formation of a new embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

. When a fertilized ovum reaches the uterus, it becomes implanted in the lining of the uterus, known as endometrium
Endometrium
-Function:The endometrium is the innermost glandular layer and functions as a lining for the uterus, preventing adhesions between the opposed walls of the myometrium, thereby maintaining the patency of the uterine cavity. During the menstrual cycle or estrous cycle, the endometrium grows to a...

, and a pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 begins. Unlike most species, human sexual activity is not linked to periods of estrus and can take place at any time during the reproductive cycle, even during pregnancy. Where a sperm donor has sexual intercourse with a woman who is not his partner, for the sole purpose of impregnating the woman, this practice may be known as natural insemination
Insemination
Insemination is the deliberate introduction of sperm into the uterus of a mammal or the oviduct of an oviparous animal for the objective of impregnating a female for reproduction...

, or NI.

Roughly six million U.S. women become pregnant per year. About two-thirds of these pregnancies result in live births and roughly 25% in abortions; the remainder end in miscarriage. The U.S. teenage pregnancy
Teenage pregnancy
Teenage pregnancy is a pregnancy of a female under the age of 20 when the pregnancy ends. It generally refers to a female who is unmarried and usually refers to an unplanned pregnancy...

 rate fell by 27 percent between 1990 and 2000, from 116.3 pregnancies per 1,000 girls aged 15–19 to 84.5. This data includes live births, abortions, and fetal losses. Almost 1 million American teenage women, 10% of all women aged 15–19 and 19% of those who have had intercourse, become pregnant each year, while Britain has been stated to have a teenage pregnancy rate similar to America's.

Reproduction methods and pregnancy also extend to gay
Gay
Gay is a word that refers to a homosexual person, especially a homosexual male. For homosexual women the specific term is "lesbian"....

 and lesbian
Lesbian
Lesbian is a term most widely used in the English language to describe sexual and romantic desire between females. The word may be used as a noun, to refer to women who identify themselves or who are characterized by others as having the primary attribute of female homosexuality, or as an...

 couples. For gay male pairings, there is the option of surrogate
Surrogacy
Surrogacy is an arrangement in which a woman carries and delivers a child for another couple or person. This woman may be the child's genetic mother , or she may carry the pregnancy to delivery after having an embryo, to which she has no genetic relationship whatsoever, transferred to her uterus...

 pregnancy; for lesbian couples, there is donor insemination
Insemination
Insemination is the deliberate introduction of sperm into the uterus of a mammal or the oviduct of an oviparous animal for the objective of impregnating a female for reproduction...

 in addition to choosing surrogate pregnancy. Further, developmental biologists have been researching and developing techniques to facilitate biological same-sex reproduction, though this has yet to be demonstrated in humans (see same-sex reproduction). Surrogacy and donor insemination remain the primary methods. Surrogacy is an arrangement in which a woman carries and delivers a child for another couple or person. The woman may be the child's genetic mother (traditional surrogacy) or she may carry a pregnancy to delivery after having another woman's eggs transferred to her uterus (gestational surrogacy). Gay and lesbian pairings who want the host to have no genetic connection to the child may choose gestational surrogacy and enter into a contract with an egg donor. Gay male couples might decide that they should both contribute semen for the in vitro fertilisation
In vitro fertilisation
In vitro fertilisation is a process by which egg cells are fertilised by sperm outside the body: in vitro. IVF is a major treatment in infertility when other methods of assisted reproductive technology have failed...

 (IVF) process, which further establishes the couple's joint intention to become parents. Lesbian couples often have contracts drafted to extinguish the legal rights of the sperm donor, while creating legal rights for the parent who is not biologically related to the child.

In addition to vaginal intercourse, sexual intercourse can encompass other forms of insertive sexual behavior, such as oral sex
Oral sex
Oral sex is sexual activity involving the stimulation of the genitalia of a sex partner by the use of the mouth, tongue, teeth or throat. Cunnilingus refers to oral sex performed on females while fellatio refer to oral sex performed on males. Anilingus refers to oral stimulation of a person's anus...

 and anal intercourse
Anal sex
Anal sex is the sex act in which the penis is inserted into the anus of a sexual partner. The term can also include other sexual acts involving the anus, including pegging, anilingus , fingering, and object insertion.Common misconception describes anal sex as practiced almost exclusively by gay men...

. Sexual acts, other than as a means of reproduction, are varied: Oral sex consists of all the sexual activities that involve the use of the mouth, tongue, and possibly throat to stimulate genitalia
Sex organ
A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, cones are the reproductive...

. It is sometimes performed to the exclusion of all other forms of sexual activity, and may include the ingestion or absorption of semen or vaginal fluids. While there are many sexual acts involving the anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...

, anal cavity, sphincter valve and/or rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...

, the most common meaning of anal sex is the insertion of a man's penis into another person's rectum.

Non-penetrative sex
Non-penetrative sex
Non-penetrative sex is sexual activity without vaginal, anal, or oral penetration, as opposed to the penetrative aspects of those activities...

 acts are also common. These acts are sometimes seen among heterosexuals
Heterosexuality
Heterosexuality is romantic or sexual attraction or behavior between members of the opposite sex or gender. As a sexual orientation, heterosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, physical or romantic attractions to persons of the opposite sex";...

 as maintaining "technical virginity." Some gay men view frot
Frot
Frot is a slang term derived from frottage describing a form of non-penetrative male/male sex that usually but not always involves direct penis-to-penis contact....

ting and oral sex as maintaining their virginity, while others consider the acts to be their main form of intercourse. The phrase "to have sex" can mean any or all of these behaviors (intercourse and outercourse), and there are a number of sex positions
Sex positions
Sex positions are positions which people may adopt during or for the purpose of sexual intercourse or other sexual activities. Sexual acts are generally described by the positions the participants adopt in order to perform those acts...

.

Prevalence, safe sex, and contraception

By their late teenage years, at least 3/4 of all men and women have had intercourse, and more than 2/3 of all sexually experienced teens have had 2 or more partners. Among sexually active 15- to 19-year-olds in the U.S., 83% of females and 91% of males reported using at least one method of birth control during last intercourse.

There are a variety of safe sex
Safe sex
Safe sex is sexual activity engaged in by people who have taken precautions to protect themselves against sexually transmitted diseases such as AIDS. It is also referred to as safer sex or protected sex, while unsafe or unprotected sex is sexual activity engaged in without precautions...

 practices, including non-penetrative sex
Non-penetrative sex
Non-penetrative sex is sexual activity without vaginal, anal, or oral penetration, as opposed to the penetrative aspects of those activities...

 acts, and heterosexual couples may use oral or anal sex (or both) as a means of contraception. In 2004, the Guttmacher Institute
Guttmacher Institute
The Guttmacher Institute is a non-profit organization which works to advance sexual and reproductive health. The institute operates in the United States and globally "through an interrelated program of social science research, policy analysis and public education." According to their mission...

 indicated in 2002 that 62% of the 62 million women aged 15–44 are currently using a contraceptive method, that among U.S. women who practice contraception, the Pill is the most popular choice (30.6%), followed by tubal sterilization (27.0%) and the male condom (18.0%), and that 27% of teenage women using contraceptives choose condoms as their primary method.

In 2006, a survey conducted by The Observer
The Observer
The Observer is a British newspaper, published on Sundays. In the same place on the political spectrum as its daily sister paper The Guardian, which acquired it in 1993, it takes a liberal or social democratic line on most issues. It is the world's oldest Sunday newspaper.-Origins:The first issue,...

showed that most adolescents in Britain were waiting longer to have sexual intercourse than they were only a few years earlier. In 2002, 32% of British teenagers were having sex before the age of 16; in 2006, it was only 20%. The average age a teen lost his/her virginity was 17.13 years in 2002; in 2006, it was 17.44 years on average for girls and 18.06 for boys. The most notable drop among teens who reported having sex was 14- and 15-year-olds. A 2008 survey conducted by YouGov
YouGov
YouGov, formerly known as PollingPoint in the United States, is an international internet-based market research firm launched in the UK in May 2000 by Stephan Shakespeare, now Chief Executive Officer, and Nadhim Zahawi...

 for Channel 4
Channel 4
Channel 4 is a British public-service television broadcaster which began working on 2 November 1982. Although largely commercially self-funded, it is ultimately publicly owned; originally a subsidiary of the Independent Broadcasting Authority , the station is now owned and operated by the Channel...

 showed that 40% of all 14- to 17-year-olds are sexually active, 74% of sexually active 14- to 17-year-olds have had a sexual experience, and 6% of teens would wait until marriage before having sex. Sexually transmitted infections are also on the increase in Britain. One in nine sexually active teens has chlamydia and 790,000 teens have sexually transmitted infections. In 2006, The Independent
The Independent
The Independent is a British national morning newspaper published in London by Independent Print Limited, owned by Alexander Lebedev since 2010. It is nicknamed the Indy, while the Sunday edition, The Independent on Sunday, is the Sindy. Launched in 1986, it is one of the youngest UK national daily...

newspaper reported that the biggest rise in sexually transmitted infections was in syphilis, which rose by more than 20%, while increases were also seen in cases of genital warts and herpes.

The National Survey of Sexual Health and Behavior
National Survey of Sexual Health and Behavior
The National Survey of Sexual Health and Behavior is a study of human sexual behavior conducted in the United States by the Center for Sexual Health Promotion at Indiana University in Bloomington. Articles based on the study were first released in a supplement to the October, 2010 issue of Journal...

 (NSSHB) indicated in 2010 that 1 of 4 acts of vaginal intercourse are condom protected in the U.S. (1 in 3 among singles), condom use is higher among black and Hispanic Americans than among white Americans and those from other racial groups, and adults using a condom for intercourse were just as likely to rate the sexual extent positively in terms of arousal, pleasure and orgasm than when having intercourse without one.

Duration

Intercourse often ends when the man has ejaculated. Thus the partner might not have time to reach orgasm
Orgasm
Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...

. In addition, many men suffer from premature ejaculation
Premature ejaculation
Premature ejaculation is a condition in which a man ejaculates earlier than he or his partner would like him to. Premature ejaculation is also known as rapid ejaculation, rapid climax, premature climax, or early ejaculation....

. Conversely, many women require a substantially longer duration of stimulation than men before reaching an orgasm.

A survey of Canadian and American sex therapists
Sex therapy
Sex therapy is the treatment of sexual dysfunction, such as non-consummation, premature ejaculation , erectile dysfunction, low libido, unwanted sexual fetishes, sexual addiction, painful sex, or a lack of sexual confidence, assisting people who are recovering from sexual assault, problems commonly...

 said that the average time for intromission was 7 minutes and that 1 to 2 minutes was too short, 3 to 7 minutes was adequate and 7 to 13 minutes desirable, while 10 to 30 minutes was too long.

Coitus difficulties

Anorgasmia
Anorgasmia
Anorgasmia, or Coughlan's syndrome, is a type of sexual dysfunction in which a person cannot achieve orgasm, even with adequate stimulation. In males the condition is often related to delayed ejaculation . Anorgasmia can often cause sexual frustration...

 is regular difficulty reaching orgasm after ample sexual stimulation, causing personal distress. This is much more common in women than men. The physical structure of the act of coitus favors penile stimulation over clitoral
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...

 stimulation. The location of the clitoris then often necessitates manual stimulation in order for the female to achieve orgasm. About 15 percent of women report difficulties with orgasm, and as many as 10 percent of women in the United States have never climaxed. Even women who orgasm on a regular basis only climax about 50 to 70 percent of the time.

Vaginismus
Vaginismus
Vaginismus, sometimes anglicized vaginism, is the German name for a condition which affects a woman's ability to engage in any form of vaginal penetration, including sexual intercourse, insertion of tampons and/or menstrual cups, and the penetration involved in gynecological examinations...

 is involuntary tensing of the pelvic floor musculature, making coitus distressing, painful, and sometimes impossible for women. It is a conditioned reflex of the pubococcygeus muscle, sometimes referred to as the "PC muscle". Vaginismus can be a vicious cycle for women, they expect to experience pain during intercourse, which then causes a muscle spasm, which leads to painful intercourse. Treatment of vaginismus often includes both psychological and behavioral techniques, including the use of vaginal dilators
Speculum (medical)
A speculum is a medical tool for investigating body cavities, with a form dependent on the body cavity for which it is designed. In old texts, the speculum may also be referred to as a diopter or dioptra...

. A new medical treatment using Botox is in the testing phase. Some women also experience dyspareunia
Dyspareunia
Dyspareunia is painful sexual intercourse, due to medical or psychological causes. The symptom is reported almost exclusively by women, although the problem can also occur in men. The causes are often reversible, even when long-standing, but self-perpetuating pain is a factor after the original...

, a medical term for painful or uncomfortable intercourse, of unknown cause.

About 40% of males suffer from some form of erectile dysfunction
Erectile dysfunction
Erectile dysfunction is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance....

 (ED) or impotence, at least occasionally. For those whose impotence is caused by medical conditions, prescription drugs such as Viagra, Cialis, and Levitra are available. However, doctors caution against the unnecessary use of these drugs because they are accompanied by serious risks such as increased chance of heart attack. Moreover, using a drug to counteract the symptom—impotence—can mask the underlying problem causing the impotence and does not resolve it. A serious medical condition might be aggravated if left untreated.

A more common sexual disorder in males is premature ejaculation
Premature ejaculation
Premature ejaculation is a condition in which a man ejaculates earlier than he or his partner would like him to. Premature ejaculation is also known as rapid ejaculation, rapid climax, premature climax, or early ejaculation....

 (PE). The American Urological Association
American Urological Association
The American Urological Association is a professional association in the United States for urology professionals.-Awards:*Hugh Hampton Young Award. Presented annually to an individual for outstanding contributions to the study of genitourinary tract disease. This award is sponsored by Karl Storz...

 (AUA) estimates that premature ejaculation could affect 21 percent of men in the United States. The U.S. Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 is examining the drug dapoxetine
Dapoxetine
Dapoxetine is a short-acting selective serotonin reuptake inhibitor marketed for the treatment of premature ejaculation in men. Dapoxetine is the only drug with regulatory approval for such an indication. Currently, it is approved in several European countries, including Finland, Sweden,...

 to treat premature ejaculation. In clinical trials, those with PE who took dapoxetine experienced intercourse three to four times longer before orgasm than without the drug. Another ejaculation-related disorder is delayed ejaculation
Delayed ejaculation
Delayed ejaculation is the inability to ejaculate or persistent difficulty in achieving orgasm despite the presence of normal sexual desire and sexual stimulation...

, which can be caused as an unwanted side effect of antidepressant medications such as Fluvoxamine
Fluvoxamine
Fluvoxamine is an antidepressant which functions as a selective serotonin reuptake inhibitor . Fluvoxamine was first approved by the U.S. Food and Drug Administration in 1993 for the treatment of obsessive compulsive disorder . Fluvoxamine CR is approved to treat social anxiety disorder...

.

Although disability
Disability
A disability may be physical, cognitive, mental, sensory, emotional, developmental or some combination of these.Many people would rather be referred to as a person with a disability instead of handicapped...

-related pain and mobility impairment can hamper intercourse, in many cases the most significant impediments to intercourse for individuals with a disability are psychological. In particular, people who have a disability can find intercourse daunting due to issues involving their self-concept
Self-concept
Self-concept is a multi-dimensional construct that refers to an individual's perception of "self" in relation to any number of characteristics, such as academics , gender roles and sexuality, racial identity, and many others. Each of these characteristics is a research domain Self-concept (also...

 as a sexual being, or partner's discomfort or perceived discomfort.

Temporary difficulties can arise with alcohol and sex
Alcohol and sex
Alcohol consumption has a number of effects on sexual intercourse and sexual behavior. The effects of alcohol are a balance between its suppressive effects on sexual physiology, which will decrease sexual activity, and its suppression of psychological inhibitions, which will increase the desire for...

 as alcohol initially increases interest (through disinhibition) but decreases capacity with greater intake.

Benefits

In humans, sex has been claimed to produce health benefits as varied as improved sense of smell, stress
Stress (biology)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...

 and blood pressure reduction,
increased immunity
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

, and decreased risk of prostate cancer
Prostate cancer
Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...

. Sexual intimacy, as well as orgasms, increases levels of the hormone oxytocin
Oxytocin
Oxytocin is a mammalian hormone that acts primarily as a neuromodulator in the brain.Oxytocin is best known for its roles in sexual reproduction, in particular during and after childbirth...

, also known as "the love hormone", which helps people bond and build trust. A long-term study of 3,500 people between 30 and 101 by clinical neuropsychologist David Weeks, MD, head of old age psychology at the Royal Edinburgh Hospital in Scotland, found that "sex helps you look between four and seven years younger", according to impartial ratings of the subjects' photos. Exclusive causation, however, is unclear, and the benefits may be indirectly related to sex and directly related to significant reductions in stress, greater contentment, and better sleep that sex promotes.

Risks

In contrast to its benefits, sexual intercourse can also be a disease vector. There are 19 million new cases of sexually transmitted diseases (STD) every year in the U.S., and worldwide there are over 340 million STDs a year. More than half of all STDs occur in adolescents and young adults aged 15–24 years. At least one in four U.S. teenage girls has a sexually transmitted disease. In the US, about 30% of 15–17 year old adolescents have had sexual intercourse, but only about 80% of 15–19 year old adolescents report using condoms for their first sexual intercourse. More than 75% of young women age 18–25 years felt they were at low risk of acquiring an STD in one study. Some sexually transmitted infections include:
  • Chlamydia is particularly dangerous because there are many infected individuals who experience no symptoms. Left untreated, chlamydia can lead to many complications, especially for women (such as the inability to bear children later in life).
  • Hepatitis B can also be transmitted through sexual contact. The disease is most common in China and other parts of Asia where 8–10% of the adult population is infected with Hepatitis. About a third of the world's population
    World population
    The world population is the total number of living humans on the planet Earth. As of today, it is estimated to be  billion by the United States Census Bureau...

    , more than 2 billion people, have been infected with the hepatitis B virus.
  • Syphilis
    Syphilis
    Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...

     infection is on the rise in all parts of the United States
    United States
    The United States of America is a federal constitutional republic comprising fifty states and a federal district...

     and is related to about 21% of fetal and newborn deaths in sub-Saharan Africa
    Africa
    Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

    . Syphilis
    Syphilis
    Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...

     causes genital sores that make it easier to transmit and contract HIV.
  • AIDS
    AIDS
    Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

     is caused by HIV
    HIV
    Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

     which is spread primarily via sexual intercourse. The World Health Organization
    World Health Organization
    The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

     reported that in 2008, approximately 33.4 million people had HIV (about 2/3 in sub-Saharan Africa and 1.1 million in the United States) , and 2 million died of AIDS worldwide.


Safe sex
Safe sex
Safe sex is sexual activity engaged in by people who have taken precautions to protect themselves against sexually transmitted diseases such as AIDS. It is also referred to as safer sex or protected sex, while unsafe or unprotected sex is sexual activity engaged in without precautions...

 is a relevant harm reduction
Harm reduction
Harm reduction refers to a range of public health policies designed to reduce the harmful consequences associated with recreational drug use and other high risk activities...

 philosophy. Condom
Condom
A condom is a barrier device most commonly used during sexual intercourse to reduce the probability of pregnancy and spreading sexually transmitted diseases . It is put on a man's erect penis and physically blocks ejaculated semen from entering the body of a sexual partner...

s and dental dam
Dental dam
A dental dam or rubber dam is a rectangular sheet of latex used in dentistry, in particular endodontic therapy, to reduce contamination, and where dental composite are being placed, due to the need for the area to remain dry during filling placement...

s are widely recommended for the prevention of STDs. According to reports by the National Institutes of Health
National Institutes of Health
The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...

 (NIH) and World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 (WHO), correct and consistent use of latex condoms reduces the risk of HIV/AIDS transmission by approximately 85%–99% relative to risk when unprotected.

People, especially those who get little or no physical exercise, have a slightly increased risk of triggering heart attack
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

 or sudden cardiac death
Sudden Cardiac Death
Sudden cardiac death is natural death from cardiac causes, heralded by abrupt loss of consciousness within one hour of the onset of acute symptoms. Other forms of sudden death may be noncardiac in origin...

 when they engage in sexual intercourse, or any other vigorous physical exercise which is engaged in on a sporadic basis. Increased risk is temporary with incidents occurring within a few hours of the activity. Regular exercise reduces but does not eliminate the increased risk.

Adults

Alex Comfort
Alex Comfort
Alexander Comfort, MB BChir, PhD, DSc was a medical professional, gerontologist, anarchist, pacifist, conscientious objector and writer, best known for The Joy of Sex, which played a part in what is often called the sexual revolution...

 and others posit three potential advantages of intercourse in humans, which are not mutually exclusive: reproductive, relational, and recreational. While the development of the Pill and other highly effective forms of contraception
Contraception
Contraception is the prevention of the fusion of gametes during or after sexual activity. The term contraception is a contraction of contra, which means against, and the word conception, meaning fertilization...

 in the mid- and late 20th century increased people's ability to segregate these three functions, they still overlap a great deal and in complex patterns. For example: A fertile couple may have intercourse while contracepting not only to experience sexual pleasure (recreational), but also as a means of emotional intimacy (relational), thus deepening their bonding, making their relationship more stable and more capable of sustaining children in the future (deferred reproductive). This same couple may emphasize different aspects of intercourse on different occasions, being playful during one episode of intercourse (recreational), experiencing deep emotional connection on another occasion (relational), and later, after discontinuing contraception, seeking to achieve pregnancy (reproductive, or more likely reproductive and relational).

Nearly all Americans marry during their lifetime; yet close to half of all first marriages are expected to end in separation or divorce, many within a few years, and subsequent marriages are even more likely to end. Sexual dissatisfaction is associated with increased risk of divorce and relationship dissolution.

According to the National Survey of Sexual Health and Behavior
National Survey of Sexual Health and Behavior
The National Survey of Sexual Health and Behavior is a study of human sexual behavior conducted in the United States by the Center for Sexual Health Promotion at Indiana University in Bloomington. Articles based on the study were first released in a supplement to the October, 2010 issue of Journal...

 (NSSHB), in 2010, men whose most recent sexual encounter was with a relationship partner reported greater arousal, greater pleasure, fewer problems with erectile function, orgasm
Orgasm
Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...

, and less pain during the event than men whose last sexual encounter was with a non-relationship partner. According to the Journal of Counseling & Development, many women express that their most satisfying sexual experiences entail being connected to someone, rather than solely basing satisfaction on orgasm.

Adolescents

With regard to adolescent sexuality
Adolescent sexuality
Adolescent sexuality refers to sexual feelings, behavior and development in adolescents and is a stage of human sexuality. Sexuality is often a vital aspect of teenagers' lives...

, sexual intercourse is also often for relational and recreational purposes. However, teenage pregnancy
Teenage pregnancy
Teenage pregnancy is a pregnancy of a female under the age of 20 when the pregnancy ends. It generally refers to a female who is unmarried and usually refers to an unplanned pregnancy...

 is usually disparaged, and research suggests that the earlier onset of puberty
Precocious puberty
As a medical term, precocious puberty describes puberty occurring at an unusually early age. In most of these children, the process is normal in every respect except the unusually early age, and simply represents a variation of normal development. In a minority of children, the early development is...

 for children puts pressure on children and teenagers to act like adults before they are emotionally or cognitively ready, and thus are at risk to suffer from emotional distress
Stress (medicine)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...

 as a result of their sexual activities. Some studies have found that engaging in sex leaves adolescents, and especially girls, with higher levels of stress and depression. A majority of adolescents in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 have been provided with some information regarding sexuality, though there have been efforts among social conservatives in the United States government to limit sex education
Sex education
Sex education refers to formal programs of instruction on a wide range of issues relating to human sexuality, including human sexual anatomy, sexual reproduction, sexual intercourse, reproductive health, emotional relations, reproductive rights and responsibilities, abstinence, contraception, and...

 in public schools to abstinence-only sex education curricula.

One group of Canadian
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 researchers found a relationship between self esteem and sexual activity. They found that students, especially girls, who were verbally abused by teachers or rejected by their peers were more likely than other students to engage in sex by the end of the Grade 7. The researchers speculate that low self esteem increases the likelihood of sexual activity: "low self-esteem seemed to explain the link between peer rejection and early sex. Girls with a poor self-image may see sex as a way to become 'popular', according to the researchers".

In India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, there is growing evidence that adolescents are becoming more sexually active outside of marriage, which is feared to lead to an increase in the spread of HIV/AIDS
AIDS
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

 among adolescents, as well as the number of unwanted pregnancies and abortion
Abortion
Abortion is defined as the termination of pregnancy by the removal or expulsion from the uterus of a fetus or embryo prior to viability. An abortion can occur spontaneously, in which case it is usually called a miscarriage, or it can be purposely induced...

s, and add to the conflict between contemporary social values. In India, adolescents have relatively poor access to health care and education, and with cultural norms opposing extramarital sexual behavior, "these implications may acquire threatening dimensions for the society and the nation".

Not all views on adolescent sexual behavior are negative, however. Psychiatrist Lynn Ponton
Lynn Ponton
Dr. Lynn Elisabeth Ponton is a child and adolescent psychiatrist and professor at the University of California, San Francisco. She is the author of the books The Sex Lives of Teenagers and The Romance of Risk. Her work in the area of adolescent risk-taking has had a high profile at a time of...

 writes, "All adolescents have sex lives, whether they are sexually active with others, with themselves, or seemingly not at all," and that viewing adolescent sexuality as a potentially positive experience, rather than as something inherently dangerous, may help young people develop healthier patterns and make more positive choices regarding sex.

Ethical, moral, and legal issues

While sexual intercourse is the natural mode of reproduction for the human species, humans also have intricate moral and ethical guidelines which regulate the practice of sexual intercourse and that vary according to religious
Religion and sexuality
Most world religions have sought to address the moral issues that arise from people's sexuality in society and in human interactions. Each major religion has developed moral codes covering issues of sexuality, morality, ethics etc...

 and governmental laws. Some governments and religions also have strict designations of "appropriate" and "inappropriate" sexual behavior, which include restrictions on the types of sex acts which are permissible. (A historically prohibited and/or regulated sex act is anal sex.)

Consent and sexual offenses

Sexual intercourse with a person against their will, or without their informed legal consent
Informed consent
Informed consent is a phrase often used in law to indicate that the consent a person gives meets certain minimum standards. As a literal matter, in the absence of fraud, it is redundant. An informed consent can be said to have been given based upon a clear appreciation and understanding of the...

, is referred to as rape
Rape
Rape is a type of sexual assault usually involving sexual intercourse, which is initiated by one or more persons against another person without that person's consent. The act may be carried out by physical force, coercion, abuse of authority or with a person who is incapable of valid consent. The...

, and is considered a serious crime
Criminal law
Criminal law, is the body of law that relates to crime. It might be defined as the body of rules that defines conduct that is not allowed because it is held to threaten, harm or endanger the safety and welfare of people, and that sets out the punishment to be imposed on people who do not obey...

 in most countries. More than 90% of rape victims are female, 99% of rapists male, and only about 5% of rapists are strangers to the victims.

Most 'developed' countries have age of consent
Age of consent
While the phrase age of consent typically does not appear in legal statutes, when used in relation to sexual activity, the age of consent is the minimum age at which a person is considered to be legally competent to consent to sexual acts. The European Union calls it the legal age for sexual...

 laws specifying the minimum legal age a person may engage in sexual intercourse with substantially older persons, usually set at about 16–18, while the legal age of consent ranges from 12–20 years of age or is not a matter of law in other countries. Sex with a person under the age of consent, regardless of their stated consent, is often considered to be sexual assault
Sexual assault
Sexual assault is an assault of a sexual nature on another person, or any sexual act committed without consent. Although sexual assaults most frequently are by a man on a woman, it may involve any combination of two or more men, women and children....

 or statutory rape
Statutory rape
The phrase statutory rape is a term used in some legal jurisdictions to describe sexual activities where one participant is below the age required to legally consent to the behavior...

 depending on differences in ages of the participants.

Some countries codify rape as any sex with a person of diminished or insufficient mental capacity to give consent, regardless of age.

The expression "sexual intercourse" has been used as a term of art in England and Wales
England and Wales
England and Wales is a jurisdiction within the United Kingdom. It consists of England and Wales, two of the four countries of the United Kingdom...

 and New York State. In England and Wales, from its enactment to its repeal on the 1 May 2004, section 44 of the Sexual Offences Act 1956
Sexual Offences Act 1956
The Sexual Offences Act 1956 is an Act of the Parliament of the United Kingdom that consolidated the English criminal law relating to sexual offences between 1957 and 2004. It was mostly repealed by the Sexual Offences Act 2003 which replaced it, but sections 33 to 37 still survive. The 2003 Act...

 read:
Unnatural
This expression referred to buggery
Buggery
The British English term buggery is very close in meaning to the term sodomy, and is often used interchangeably in law and popular speech. It may be, also, a specific common law offence, encompassing both sodomy and bestiality.-In law:...

 (including both buggery with a person and buggery with an animal).

Penetration
According to cases decided on the meaning of the statutory definition of carnal knowledge
Carnal knowledge
Carnal knowledge is an archaic or legal euphemism for sexual intercourse. The term derives from the Biblical usage of the verb know/knew, as in the King James and other versions, a euphemism for sexual conduct...

 under the Offences against the Person Act 1828
Offences Against the Person Act 1828
The Offences against the Person Act 1828 was an Act of the Parliament of the United Kingdom of Great Britain and Ireland. It consolidated provisions related to offences against the person from a number of earlier statutes into a single Act...

, which was in identical terms to this definition, the slightest penetration was sufficient. The book "Archbold" said that it "submitted" that this continued to be the law under the new enactment.

Continuing act
See Kaitamaki v R [1985] AC 147, [1984] 3 WLR 137, [1984] 2 All ER 435, 79 Cr App R 251, [1984] Crim LR 564, PC
Privy council
A privy council is a body that advises the head of state of a nation, typically, but not always, in the context of a monarchic government. The word "privy" means "private" or "secret"; thus, a privy council was originally a committee of the monarch's closest advisors to give confidential advice on...

 (decided under equivalent legislation in New Zealand).

Section 7(2) of the Sexual Offences (Amendment) Act 1976
Sexual Offences (Amendment) Act 1976
The Sexual Offences Act 1976 is an Act of the Parliament of the United Kingdom. It made provision in relation to rape and related offences. Except for subsections and and and of section 7, the whole Act is repealed. Section 7 now provides the definition of the expression "a rape offence" in...

 contained the following words: "In this Act . . . references to sexual intercourse shall be construed in accordance with section 44 of the Sexual Offences Act 1956 so far as it relates to natural intercourse (under which such intercourse is deemed complete on proof of penetration only)". The Act made provision, in relation to rape and related offences, for England and Wales, and for courts-martial elsewhere.

From 3 November 1994 to 1 May 2004, section 1(2)(a) of the Sexual Offences Act 1956 (as substituted by section 142 of the Criminal Justice and Public Order Act 1994
Criminal Justice and Public Order Act 1994
The Criminal Justice and Public Order Act 1994 is an Act of the Parliament of the United Kingdom. It introduced a number of changes to the existing law, most notably in the restriction and reduction of existing rights and in greater penalties for certain "anti-social" behaviours...

) referred to "sexual intercourse with a person (whether vaginal or anal)". This section created the offence of rape in England and Wales.

The penal code in New York State provides: § 130.00 Sex offenses; definitions of terms: 1. "Sexual intercourse" has its ordinary meaning and occurs upon any penetration, however slight.

Sexual orientation and gender

There is considerable legal variability regarding definitions of and the legality of sexual intercourse between persons of the same sex and/or gender. For example, in 2003 the New Hampshire Supreme Court
New Hampshire Supreme Court
The New Hampshire Supreme Court is the supreme court of the U. S. state of New Hampshire and sole appellate court of the state. The Supreme Court is seated in the state capital, Concord. The Court is composed of a Chief Justice and four Associate Justices appointed by the Governor and Executive...

 ruled that female same-sex relations did not constitute sexual intercourse, based on a 1961 definition from Webster's Third New International Dictionary, in Blanchflower v. Blanchflower
Blanchflower v. Blanchflower
Blanchflower v. Blanchflower, 150 N.H. 226, is a landmark decision handed down by the New Hampshire Supreme Court which ruled that sexual relations between two females, one of whom is married, does not constitute adultery, because it is not technically sexual intercourse.-Background:In 2003, a...

, and thereby an accused wife in a divorce case was found not guilty of adultery based on this technicality. Some countries, such as Islamic countries, consider homosexual behavior to be an offense punishable by imprisonment or execution.

Marital status and relationships

Sexual intercourse has traditionally been considered an essential part of a marriage
Marriage
Marriage is a social union or legal contract between people that creates kinship. It is an institution in which interpersonal relationships, usually intimate and sexual, are acknowledged in a variety of ways, depending on the culture or subculture in which it is found...

; many religious customs required consummation
Consummation
Consummation is the initial sexual act made within a marriage.Consummation can also refer to:* Consummation , 1970 recordingSee also:* Consummation of days, event predicted in Daniel Chapter 12, verses 1-4...

 of the marriage by sexual intercourse, and the failure for any reason to consummate the marriage was a ground for annulment
Annulment
Annulment is a legal procedure for declaring a marriage null and void. Unlike divorce, it is usually retroactive, meaning that an annulled marriage is considered to be invalid from the beginning almost as if it had never taken place...

, which did not require a divorce process. Annulment declaration implied that the marriage was void from the start – i.e. there was in law no marriage. Furthermore, continuing sexual relations between the marriage partners is commonly considered a 'marital right' by many religions, permissible to married couples, generally for the purpose of reproduction. Today, there is wide variation in the opinions and teachings about sexual intercourse relative to marriage and other intimate relationships by the world's religions. Examples:
  • Some sections of Christianity
    Christianity
    Christianity is a monotheistic religion based on the life and teachings of Jesus as presented in canonical gospels and other New Testament writings...

    , such as Catholicism
    Catholicism
    Catholicism is a broad term for the body of the Catholic faith, its theologies and doctrines, its liturgical, ethical, spiritual, and behavioral characteristics, as well as a religious people as a whole....

    , commonly view sex in marriage as holy and for the purpose of reproduction.
  • Islam
    Islam
    Islam . The most common are and .   : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...

     views sex within marriage as something pleasurable, a spiritual activity, and a duty.
  • In Judaism
    Judaism
    Judaism ) is the "religion, philosophy, and way of life" of the Jewish people...

    , a married Jewish man is required to provide his wife with sexual pleasure called onah (literally, "her time"), which is one of the conditions he takes upon himself as part of the Jewish marriage contract, ketubah
    Ketubah
    A ketubah is a special type of Jewish prenuptial agreement. It is considered an integral part of a traditional Jewish marriage, and outlines the rights and responsibilities of the groom, in relation to the bride.-History:...

    , that he gives her during the Jewish wedding ceremony. In Jewish views on marriage, sexual desire is not evil, but must be satisfied in the proper time, place and manner.
  • In Shi'ia Islam, men are allowed to enter into an unlimited number of temporary marriages, which are contracted to last for a period of minutes to multiple years and permit sexual intercourse. Shi'ia women are allowed to enter only one marriage at a time, whether temporary or permanent.
  • Wicca
    Wicca
    Wicca , is a modern Pagan religious movement. Developing in England in the first half of the 20th century, Wicca was popularised in the 1950s and early 1960s by a Wiccan High Priest named Gerald Gardner, who at the time called it the "witch cult" and "witchcraft," and its adherents "the Wica."...

    ns believe that, as declared within the Charge of the Goddess
    Charge of the Goddess
    The Charge of the Goddess is a traditional inspirational text sometimes used in the neopagan religion of Wicca. Several versions exist, though they all have the same basic premise, that of a set of instructions given by a Great Goddess to her worshippers...

    , to “Let my [the Goddess] worship be within the heart that rejoiceth; for behold, all acts of love and pleasure are my rituals.” This statement appears to allow one freedom to explore sensuality and pleasure, and mixed with the final maxim within the Wiccan Rede
    Wiccan Rede
    The Wiccan Rede is a statement that provides the key moral system in the Neopagan religion of Wicca and other related Witchcraft-based faiths. A common form of the Rede is An it harm none, do what ye will....

     — “26. Eight words the Wiccan Rede fulfill – an’ it harm none, do what ye will.” — Wiccans are encouraged to be responsible with their sexual encounters, in whatever variety they may occur.
  • Hinduism has varied views about sexuality, but Hindu society, in general, perceives extramarital sex to be immoral and shameful.
  • Buddhist
    Buddhism
    Buddhism is a religion and philosophy encompassing a variety of traditions, beliefs and practices, largely based on teachings attributed to Siddhartha Gautama, commonly known as the Buddha . The Buddha lived and taught in the northeastern Indian subcontinent some time between the 6th and 4th...

     ethics, in its most common formulation, holds that one should neither be attached to nor crave sensual pleasure.
  • In the Bahá'í Faith
    Bahá'í Faith
    The Bahá'í Faith is a monotheistic religion founded by Bahá'u'lláh in 19th-century Persia, emphasizing the spiritual unity of all humankind. There are an estimated five to six million Bahá'ís around the world in more than 200 countries and territories....

    , sexual relationships are permitted only between a husband and wife.
  • Unitarian Universalists, with an emphasis on strong interpersonal ethics, do not place boundaries on the occurrence of sexual intercourse among consenting adults.
  • According to the Brahma Kumaris and Prajapita Brahma Kumaris religion, the power of lust
    Lust
    Lust is an emotional force that is directly associated with the thinking or fantasizing about one's desire, usually in a sexual way.-Etymology:The word lust is phonetically similar to the ancient Roman lustrum, which literally meant "purification"...

     is the root of all evil and worse than murder. Purity (celibacy
    Celibacy
    Celibacy is a personal commitment to avoiding sexual relations, in particular a vow from marriage. Typically celibacy involves avoiding all romantic relationships of any kind. An individual may choose celibacy for religious reasons, such as is the case for priests in some religions, for reasons of...

    ) is promoted for peace and to prepare for life in forthcoming Heaven on earth for 2,500 years when children will be created by the power of the mind.
  • Shakers
    Shakers
    The United Society of Believers in Christ’s Second Appearing, known as the Shakers, is a religious sect originally thought to be a development of the Religious Society of Friends...

     believe that sexual intercourse is the root of all sin and that all people should therefore be celibate, including married couples. Predictably, the original Shaker community that peaked at 6,000 full members in 1840 dwindled to three members by 2009.
  • Meher Baba
    Meher Baba
    Meher Baba , , born Merwan Sheriar Irani, was an Indian mystic and spiritual master who declared publicly in 1954 that he was the Avatar of the age....

     maintained that "In the beginning of married life the partners are drawn to each other by lust as well as love; but with conscious and deliberate cooperation they can gradually lessen the element of lust and increase the element of love. Through this process of sublimation, lust ultimately gives place to deep love."


In some cases, the sexual intercourse between two people is seen as counter to religious law or doctrine. In many religious communities, including the Catholic Church and Mahayana Buddhists
Bhikkhu
A Bhikkhu or Bhikṣu is an ordained male Buddhist monastic. A female monastic is called a Bhikkhuni Nepali: ). The life of Bhikkhus and Bhikkhunis is governed by a set of rules called the patimokkha within the vinaya's framework of monastic discipline...

, religious leaders are expected to refrain from sexual intercourse in order to devote their full attention, energy, and loyalty to their religious duties.

Opposition to same-sex marriage
Same-sex marriage
Same-sex marriage is marriage between two persons of the same biological sex or social gender. Supporters of legal recognition for same-sex marriage typically refer to such recognition as marriage equality....

 is largely based on the belief that sexual intercourse and sexual orientation should be of a heterosexual nature. The recognition of such marriages is a civil rights, political, social, moral, and religious issue in many nations, and the conflicts arise over whether same-sex couples should be allowed to enter into marriage, be required to use a different status (such as a civil union, which either grant equal rights as marriage or limited rights in comparison to marriage), or not have any such rights. A related issue is whether the term marriage should be applied.

In other animals

In zoology, copulation is often termed as the process in which a male introduces sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...

 into the female's body. Spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...

s have separate male and female sexes. Before mating and copulation, a male spins a small web and ejaculates on to it. He then stores the sperm in reservoirs on his large pedipalp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...

s, from which he transfers sperm to the female's genitals. Females can store sperm indefinitely.

Many animals which live in the water use external fertilization
External fertilization
External fertilization is a form of fertilization in which a sperm cell is united with an egg cell external to the bodies of the reproducing individuals. In contrast, internal fertilization takes place inside the female after insemination through copulation....

, whereas internal fertilization
Internal fertilization
In mammals, internal fertilization is done through copulation, which involves the insertion of the penis into the vagina. Some other higher vertebrate animals reproduce internally, but their fertilization is cloacal.The union of spermatozoa of the parent organism. At some point, the growing egg or...

 may have developed from a need to maintain gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...

s in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates (such as reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s, some fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, and most bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s) occur via cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...

l copulation (see also hemipenis
Hemipenis
A hemipenis is one of a pair of intromittent organs of male squamates .Hemipenes are usually held inverted, within the body, and are everted for reproduction via erectile tissue, much like that in the human penis. Only one is used at a time, and some evidence indicates males alternate use between...

), while mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s copulate vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

lly, and many basal
Primitive (biology)
Primitive in the sense most relevant to phylogenetics means resembling the first living things and in particular resembling them in the simple nature of their anatomy and behaviour...

 vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s reproduce sexually with external fertilization.

However, some terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...

 arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s do use external fertilization. For primitive insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, the male deposits spermatozoa
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...

 on the substrate, sometimes stored within a special structure, and courtship
Courtship
Courtship is the period in a couple's relationship which precedes their engagement and marriage, or establishment of an agreed relationship of a more enduring kind. In courtship, a couple get to know each other and decide if there will be an engagement or other such agreement...

 involves inducing the female to take up the sperm package into her genital opening; there is no actual copulation. In groups such as dragonflies and spiders, males extrude sperm into secondary copulatory structures removed from their genital opening, which are then used to inseminate the female (in dragonflies, it is a set of modified sternites on the second abdominal segment; in spiders, it is the male pedipalp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...

s). In advanced groups of insects, the male uses its aedeagus
Aedeagus
An aedeagus is a reproductive organ of male insects through which they secrete sperm from the testes during copulation with a female insect...

, a structure formed from the terminal segments of the abdomen, to deposit sperm directly (though sometimes in a capsule called a "spermatophore
Spermatophore
A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...

") into the female's reproductive tract.

Humans, bonobos, chimpanzees and dolphins are species known to engage in heterosexual behaviors even when the female is not in estrus, which is a point in her reproductive cycle suitable for successful impregnation. These species, and others, are also known to engage in homosexual behaviors. Humans, bonobos and dolphins are all intelligent social animals, whose cooperative behavior proves far more successful than that of any individual alone. In these animals, the use of sex has evolved beyond reproduction, to apparently serve additional social functions. Sex reinforces intimate social bonds between individuals to form larger social structures. The resulting cooperation encourages collective tasks that promote the survival of each member of the group.

See also

  • Erogenous zone
    Erogenous zone
    An erogenous zone is an area of the human body that has heightened sensitivity, the stimulation of which may result in the production of erotic sensations or sexual excitement.People have erogenous zones all over their bodies, but which areas are more sensitive than others vary...

  • Human sexual response cycle
    Human sexual response cycle
    The human sexual response cycle is a four-stage model of physiological responses during sexual stimulation. These phases, in order of their occurrence, are the excitement phase, plateau phase, orgasmic phase, and resolution phase. The term was coined by William H. Masters and Virginia E...

  • Public sex
    Public sex
    Public sex refers to sexual acts that take place in public or semi-public places, and does not necessarily imply that the sexual activity takes place outdoors. Public places where sex acts can be performed include a car , on a beach, in the woods, as well as in a theatre, bus, street, besides...

  • Sexological testing
    Sexological testing
    Sexuality can be inscribed in a multidimensional model comprising different aspects of human life: biology, reproduction, culture, entertainment, relationships and love....



External links

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