ceremony vs social gathering

ceremony and social gathering both are nouns.

Word	Noun	Adjective	Verb	Adverb
ceremony	Yes	No	No	No
social gathering	Yes	No	No	No

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

ceremony: a formal event performed on a special occasion
social gathering: a formal or official social gathering or ceremony of people

Other hypernyms of ceremony include affair, function, occasion, social affair, social function, social occasion.

ceremony (noun)	social gathering (noun)
the proper or conventional behavior on some solemn occasion	a formal or official social gathering or ceremony of people
any activity that is performed in an especially solemn elaborate or formal way
a formal event performed on a special occasion