Baptism (from the Greek noun βάπτισμα báptisma) is a Christian rite of admission and adoption, almost invariably with the use of water, into Christianity. It may be performed by sprinkling or pouring water on the head, or by immersing in water either partially or completely. The synoptic gospels recount that John the Baptist baptised Jesus. Baptism is considered a sacrament in most churches, and as an ordinance in others. 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. Baptism is also called christening, although some reserve the word "christening" for the baptism of infants. It has also given its name to the Baptist churches and denominations.