A term used by Latin Catholics and some high-church Anglicans for a worship service that includes the celebration of Holy Communion. The term cannot be used for services that do not include Communion, including those in which someone distributes Communion hosts that were consecrated outside of that service. Catholic sources say a Mass is celebrated or said; however, The Associated Press accepts only celebrated. Capitalize when referring to the celebration of worship in the Roman Catholic Church. Lowercase any preceding adjectives, as in funeral Mass. Orthodox Christians call their Eucharistic service the Divine Liturgy.
REFERENCE: Religion Stylebook