Baptism (from Koine Greek: βάπτισμα, romanized: váptisma, lit. 'immersion, dipping in water') is a Christian rite of initiation almost invariably with the use of water. It may be performed by sprinkling or pouring water on the head, or immersing in water (partially or completely), traditionally three times for each person of the Trinity. It is also called christening, although this is typically reserved for the baptism of infants. Baptism is regarded as a sacrament in most churches and an ordinance in others, with the synoptic gospels recounting that John the Baptist baptized Jesus.
Baptism according to the Trinitarian formula, which is done in most mainstream Christian denominations, is seen as being a basis for Christian ecumenism, the concept of unity amongst Christians. In certain Christian denominations, such as the Catholic Churches, Eastern Orthodox Churches, Oriental Orthodox Churches, Assyrian Church of the East, and Lutheran Churches, baptism is the door to church membership, with candidates taking baptismal vows. It has also given its name to the Baptist churches and denominations.