REQUIEM, the name of a solemn mass for the dead (Missa pro defunctis) in the Roman Church, appointed to be sung on All Souls' Day, in memory of all " faithful departed," at funeral services, and at the anniversaries of the death of particular persons. The name is taken from the first words of the Introit, Requiem aeternam dona eis, Domine. The term is specially applied to the musical setting of the mass. The most celebrated Requiem Masses are those of Palestrina, Mozart and Cherubini. The word has been also used of memorial services held in honour of a deceased person in churches other than the Roman.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)