ceremony vs ceremonial occasion

ceremony and ceremonial occasion both are nouns.

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

As nouns, ceremony and ceremonial occasion are synonyms defined as:

ceremony and ceremonial occasion: a formal event performed on a special occasion

Other synonyms of ceremony include ceremonial, observance.

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