.]]The Requiem (from Latin requiem, accusative case of requies, rest) or Requiem Mass (informally, a funeral Mass), also known formally (in Latin) as the Missa pro defunctis or Missa defunctorum, is a liturgical service of the Roman Catholic Church, Anglo-Catholic and High Church Anglicans, as well as 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 th
Source:
http://en.wikipedia.org/wiki/Requiem