ceremony vs social occasion

ceremony and social occasion both are nouns.

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

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

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

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

ceremony (noun)	social occasion (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