observance vs observe

observance is a noun but observe is not a noun.

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

observance (noun)	observe (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

observance (verb)	observe (verb)
	stick to correctly or closely
	make mention of
	watch attentively
	observe with care or pay close attention to
	discover or determine the existence, presence, or fact of by perception with the eyes
	follow with the eyes or the mind
	show respect towards
	behave as expected during of holidays or rites
	conform one's action or practice to