A soulmate is believed by some to be the person with whom one has a feeling of deep or natural affinity

Affinity (sociology)

Affinity in terms of sociology, refers to "kinship of spirit", interest and other interpersonal commonalities. Affinity is characterized by high levels of intimacy and sharing, usually in close groups, also known as affinity groups. It differs from affinity in law and canon law which generally...

, similarity, love

Love

Love is an emotion of strong affection and personal attachment. In philosophical context, love is a virtue representing all of human kindness, compassion, and affection. Love is central to many religions, as in the Christian phrase, "God is love" or Agape in the Canonical gospels...

, intimacy, sexuality

Human sexuality

Human sexuality is the awareness of gender differences, and the capacity to have erotic experiences and responses. Human sexuality can also be described as the way someone is sexually attracted to another person whether it is to opposite sexes , to the same sex , to either sexes , or not being...

, spirituality

Spirituality

Spirituality can refer to an ultimate or an alleged immaterial reality; an inner path enabling a person to discover the essence of his/her being; or the “deepest values and meanings by which people live.” Spiritual practices, including meditation, prayer and contemplation, are intended to develop...

, or compatibility

Interpersonal compatibility

Interpersonal compatibility is a concept that describes the long-term interaction between two or more individuals in terms of the ease and comfort of communication.-Existing concepts:...

. A related concept is that of the twin flame or twin soul, which is thought to be the ultimate soulmate. In New Age

New Age

The New Age movement is a Western spiritual movement that developed in the second half of the 20th century. Its central precepts have been described as "drawing on both Eastern and Western spiritual and metaphysical traditions and then infusing them with influences from self-help and motivational...

 spirituality, the ultimate soulmate is the one and only other half of one's soul

Soul

A soul in certain spiritual, philosophical, and psychological traditions is the incorporeal essence of a person or living thing or object. Many philosophical and spiritual systems teach that humans have souls, and others teach that all living things and even inanimate objects have souls. The...

..
In his dialogue The Symposium

Symposium (Plato)

The Symposium is a philosophical text by Plato dated c. 385–380 BCE. It concerns itself at one level with the genesis, purpose and nature of love....

, Plato

Plato

Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

 has Aristophanes

Aristophanes

Aristophanes , son of Philippus, of the deme Cydathenaus, was a comic playwright of ancient Athens. Eleven of his forty plays survive virtually complete...

 present a story about soulmates.