Octave (liturgical)

"Octave" has two senses in Christian liturgical usage. In the first sense, it is the eighth day after a feast, reckoning inclusively, and so always falls on the same day of the week as the feast itself. The word is derived from Latin octava (eighth), with dies (day) understood. The term is also applied to the whole period of these eight days, during which the observance of certain major feasts came to be observed.Oxford Dictionary of the Christian Church (Oxford University Press 2005 ISBN 978-0-19-280290-3), article Octave

Octaves are not to be confused with eight-day weeks: see Christian "eighth day".

From origin to Middle Ages

The practice may have had its origins in the Old Testament eight-day celebration of the Feast of Tabernacles () and the Dedication of the Temple (). However, the number "eight" may also be a reference to the Resurrection, which in the early church was often referred to as the "eighth day". The "eighth day" may also refer to the "new creation" following the second coming of Christ, which is beyond time.

For this reason, early Christian baptistries and tombs typically were shaped as octagons. The practice of octaves was first introduced under Constantine I, when the dedication festivities of the basilicas at Jerusalem and Tyre, Lebanon were observed for eight days. After these one-off occasions, annual liturgical feasts began to be dignified with...
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