An officiant is someone who officiates (i.e. leads) at a service or ceremony, such as 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...

, burial

Burial

Burial is the act of placing a person or object into the ground. This is accomplished by excavating a pit or trench, placing an object in it, and covering it over.-History:...

, or namegiving/baptism

Baptism

In Christianity, baptism is for the majority the rite of admission , almost invariably with the use of water, into the Christian Church generally and also membership of a particular church tradition...

. Officiants may be ordained by any denomination as members of their clergy, or by secular/Humanist or interfaith/interspiritual religious bodies. Officiants differ from Chaplains in that Officiants serve the unaffiliated public at large, while Chaplains are usually employed by an institution such as the military, a hospital or other health care facility, etc. The term "Officiant" includes Justices of the Peace, celebrant

Celebrant

Celebrant may refer to:* Celebrant or Officiant, the leader of a liturgy or ceremony who is empowered to perform it** In the Catholic and Anglican churches, the celebrant is the person who celebrates a sacrament, e.g., the priest who celebrates the Eucharist or the bishop who ordains a priest*...

s, marriage commissioners

Deputy marriage commissioner

The duties of a Deputy Marriage Commissioner vary from county to county and from state to state within the United States but are generally empowered to perform Civil Marriage ceremonies during a fixed time and/or in a fixed place...

, ministers, notaries, and other people empowered by law to perform legally binding private ceremonies.

Ordination is a requirement in a number of jurisdiction

Jurisdiction

Jurisdiction is the practical authority granted to a formally constituted legal body or to a political leader to deal with and make pronouncements on legal matters and, by implication, to administer justice within a defined area of responsibility...

s to officiate at wedding

Wedding

A wedding is the ceremony in which two people are united in marriage or a similar institution. Wedding traditions and customs vary greatly between cultures, ethnic groups, religions, countries, and social classes...

s, but each state, province and country has their own laws. In places where ordination is not required by secular law

Law

Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

, it is left to the requirements of the particular religious denomination

Religious denomination

A religious denomination is a subgroup within a religion that operates under a common name, tradition, and identity.The term describes various Christian denominations...

 or church

Church Body

A local church is a Christian religious organization that meets in a particular location. Many are formally organized, with constitutions and by-laws, maintain offices, are served by pastors or lay leaders, and, in nations where this is permissible, often seek seek non-profit corporate status...

 whether ordination is required.

Some Officiants work within congregations in some denominations as non-ordained members on the Clergy team. While an officiant or celebrant

Celebrant

Celebrant may refer to:* Celebrant or Officiant, the leader of a liturgy or ceremony who is empowered to perform it** In the Catholic and Anglican churches, the celebrant is the person who celebrates a sacrament, e.g., the priest who celebrates the Eucharist or the bishop who ordains a priest*...

 at a sacrament

Sacrament

A sacrament is a sacred rite recognized as of particular importance and significance. There are various views on the existence and meaning of such rites.-General definitions and terms:...

must be ordained

Ordination

In general religious use, ordination is the process by which individuals are consecrated, that is, set apart as clergy to perform various religious rites and ceremonies. The process and ceremonies of ordination itself varies by religion and denomination. One who is in preparation for, or who is...

, the same is not true of an officiant at other services. Duties of an officiant leading congregational worship vary among denominations. A common duty is to give the congregation cues when to bow during the doxology

Doxology

A doxology is a short hymn of praises to God in various Christian worship services, often added to the end of canticles, psalms, and hymns...

, to read from Scripture, and to call general prayers, e.g.,

Officiant: In the name of the Father, and of the Son, and of the Holy Spirit.

All: Amen

Amen

The word amen is a declaration of affirmation found in the Hebrew Bible and New Testament. Its use in Judaism dates back to its earliest texts. It has been generally adopted in Christian worship as a concluding word for prayers and hymns. In Islam, it is the standard ending to Dua and the...

.

etc....