observance vs observation

observance and observation both are nouns.

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

As nouns, observance and observation are synonyms defined as:

Other synonyms of observance include watching.

As nouns, observance and observation are synonyms defined as:

Other synonyms of observance include notice.

observance (noun)	observation (noun)
the act of observing; taking a patient look	the act of observing; taking a patient look
conformity with law or custom or practice etc.	the act of making and recording a measurement
the act of noticing or paying attention	the act of noticing or paying attention
a formal event performed on a special occasion	facts learned by observing
	a remark expressing careful consideration