A Requiem (or Requiem Mass) is a Eucharist service in the Roman Catholic Church to pray for the repose of the soul of someone who has died. There are special words for a Requiem Mass. They are in Latin. The best-known part of the Requiem Mass starts with the words “Requiem aeternam dona eis, Domine” (“Give them eternal rest, O Lord”). This is why it is called a “Requiem”.