observance vs social affair

observance and social affair both are nouns.

Word	Noun	Adjective	Verb	Adverb
observance	Yes	No	No	No
social affair	Yes	No	No	No

As nouns, social affair is a hypernym of observance; that is, social affair is a word with a broader meaning than observance:

Other hypernyms of observance include affair, function, occasion, social function, social gathering, social occasion.

observance (noun)	social affair (noun)
the act of observing; taking a patient look	a formal or official social gathering or ceremony of people
conformity with law or custom or practice etc.
the act of noticing or paying attention
a formal event performed on a special occasion