observant vs observance

observant is not a noun while observance is a noun.

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

observant (noun)	observance (noun)
	the act of observing; taking a patient look
	conformity with law or custom or practice etc.
	the act of noticing or paying attention
	a formal event performed on a special occasion

observant (adjective)	observance (adjective)
paying close attention especially to details
(of individuals) adhering strictly to laws and rules and customs
quick to notice; showing quick and keen perception