observance

noun

1. an act or instance of following, obeying, or conforming to: the observance of traffic laws.
2. a keeping or celebration by appropriate procedure, ceremonies, etc.: the observance of the Sabbath.
3. a procedure, ceremony, or rite, as for a particular occasion: patriotic observances.
4. a rule or custom to be followed or obeyed; a customary practice.
5. Roman Catholic Church.
   1. a rule or discipline for a religious house or order.
   2. a house or order observing a rule or discipline.
6. an act or instance of watching, noting, or perceiving; observation.
7. respectful attention or service.
8. Archaic. courteous attention as to a person; dutiful service.

noun

1. recognition of or compliance with a law, custom, practice, etc
2. the act of such recognition
3. a ritual, ceremony, or practice, esp of a religion
4. observation or attention
5. the degree of strictness of a religious order or community in following its rule
6. archaic respectful or deferential attention

n.early 13c., “act performed in accordance with prescribed usage,” especially a religious or ceremonial one, from Old French observance, osservance “observance, discipline,” or directly from Latin observantia “act of keeping customs, attention, respect, regard, reverence,” from observantem (nominative observans), present participle of observare (see observe). Observance is the attending to and carrying out of a duty or rule. Observation is watching, noticing.