a service, celebration, etc., in memory of some person or event.
3.
a memorial.
4.
(in many Christian churches) a special service or prayer for commemorating the lesser feast on days on which two feasts of unequal rank are celebrated.
Origin: 1350–1400;Middle English (< Middle French) < Latincommemorātiōn- (stem of commemorātiō), equivalent to commemorāt(us) (see commemorate) + -iōn--ion
late 14c., from O.Fr. commemoration, from L. commemorationem, from commemorare "to call to mind," from com- intens. prefix + memorare "to remind," from memor "mindful of" (see memory).