sleepover vs social affair

sleepover and social affair both are nouns.

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

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

sleepover: an occasion of spending a night away from home or having a guest spend the night in your home (especially as a party for children)
social affair: a formal or official social gathering or ceremony of people

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

sleepover (noun)	social affair (noun)
an occasion of spending a night away from home or having a guest spend the night in your home (especially as a party for children)	a formal or official social gathering or ceremony of people