Lucernarium is the singular form and Lucernaria the plural of the Latin word for "light." In the BOS and The Hymnal 1982 (S 305-S 320 in the Accompaniment Edition, Vol. 1), the term is used for the optional anthems which may be sung during the lighting of candles in the Order of Worship for the Evening (BCP, p. 109). These anthems, which vary with the season, were used at the lighting of the evening light in old Gallican liturgies.
Glossary definitions provided courtesy of Church Publishing Incorporated, New York, NY,(All Rights reserved) from "An Episcopal Dictionary of the Church, A User Friendly Reference for Episcopalians," Don S. Armentrout and Robert Boak Slocum, editors.