observance

noun

1. the act or practice of observing, or keeping, a law, duty, custom, rule, etc.
2. a customary act, rite, ceremony, etc.
3. the act of observing, or noting; observation
4. Archaic respectful attention; deference
5. R.C.Ch.
   1. the rule observed by a religious order
   2. the order observing a specified rule

Origin: ME observaunce < OFr observance < L observantia, attention, regard, in LL(Ec), divine worship