Office of the Dead
An office, originally consisting only of Vespers, Matins, and Lauds, formulated at Rome prior to the 8th century and recited in connection with funeral obsequies.
Its use spread with the Roman Breviary, and as a supplementary part of the Office it was frequently recited.
Later it became a complete office for all the Canonical Hours to be recited on 2 November, All Souls' Day.
The earlier form is recited today in many monastic communities in addition to the office of the day.
It is also frequently chanted before a funeral Mass.
New Catholic Dictionary