observance vs formality

observance and formality both are nouns.

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

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

observance (noun)	formality (noun)
the act of observing; taking a patient look	compliance with formal rules
conformity with law or custom or practice etc.	a manner that strictly observes all forms and ceremonies
the act of noticing or paying attention	a requirement of etiquette or custom
a formal event performed on a special occasion