Is it ensure, insure, or assure?
"outward and visible sign of inward and spiritual grace," also "the eucharist," c.1200, from Old French sacrament "consecration; mystery" (12c., Modern French sacrement) and directly from Latin sacramentum "a consecrating" (also source of Spanish sacramento, German Sakrament, etc.), from sacrare "to consecrate" (see sacred); a Church Latin loan-translation of Greek mysterion (see mystery).
Meaning "a holy mystery" in English is from late 14c. The seven sacraments are baptism, penance, confirmation, holy orders, the Eucharist, matrimony, and anointing of the sick (extreme unction).
A religious ceremony or rite. Most Christian churches reserve the term for those rites that Jesus himself instituted, but there are disagreements between them on which rites those are. The Lutheran Church, for example, maintains that baptism and Communion are the only sacraments, whereas in the Roman Catholic Church and the Eastern Orthodox Church, there are five more: confirmation; confession; anointing of the sick; the ordination of clergy; and the marriage of Christians.