commemoration

Short definition from Wiktionary

Noun

1. 1
   The act of commemorating; an observance or celebration to honor the memory of some person or event.
2. 2
   That which serves the purpose of commemorating; a memorial.
3. 3
   The specification of individual saints in the prayers for the dead.
4. 4
   The great festival of the Oxford academic year, usually taking place on the third Wednesday after Trinity Sunday.