The Oxford Thesaurus An A-Z Dictionary of Synonyms - observancen.

1) observation, observing, obedience, obeying, compliance, complying, conformity, conforming, adherence, adhering, keeping, accordance, regard, recognition, recognizing, respect, respecting, heed, heeding, attention: Observance of the rules by everyone makes for a happier community. 2) ceremony, celebration, ceremonial, practice, rite, ritual, service, performance, form, custom, convention, tradition, formality, usage, habit, wont, institution: Almost all the fine arts derived their origin from religious observances. 3) observation, examination, inspection, scrutiny, looking, watching: His observance of the passing scene was chronicled in his diary.