The Requiem (from the Latin requiés, rest) or Requiem Mass (informally, the funeral Mass), also known formally (in Latin) as the Missa pro defunctis or Missa defunctorum, is a liturgical service of the Roman Catholic Church as well as the Anglican/ Episcopalian "High" Church and certain Lutheran Churches in the United States. There is also a requiem, with a wholly different ritual form and texts, that is observed in the Eastern Orthodox and Eastern Catholic Churches. The common theme of requiems is prayer for the salvation of the soul(s) of the departed, and it is used both at services immediately preceding a burial, and on occasions of more general remembrance.
"Requiem" is also the title of various musical compositions used in such liturgical services or as concert pieces as settings of the portions of that Mass which have been traditionally sung in the Roman Catholic liturgy.
While the prayers in the regular Mass as the Introit and Gradual change according to the Calendar of Saints, the text for the requiem Mass is particularly fixed. Originally such funeral musical compositions were meant to be performed in liturgical service, with monophonic chant. Eventually the dramatic character began to appeal to composers to an extent that made the requiem a genre of its own.