ceremony vs formality

ceremony and formality both are nouns.

Word	Noun	Adjective	Verb	Adverb
ceremony	Yes	No	No	No
formality	Yes	No	No	No

As nouns, formality is a hyponym of ceremony; that is, formality is a word with a more specific, narrower meaning than ceremony:

ceremony (noun)	formality (noun)
the proper or conventional behavior on some solemn occasion	compliance with formal rules
any activity that is performed in an especially solemn elaborate or formal way	a manner that strictly observes all forms and ceremonies
a formal event performed on a special occasion	a requirement of etiquette or custom