circumstance vs observance

circumstance and observance both are nouns.

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

As nouns, observance is a hypernym of circumstance; that is, observance is a word with a broader meaning than circumstance:

Other hypernyms of circumstance include ceremonial, ceremonial occasion, ceremony.

circumstance (noun)	observance (noun)
information that should be kept in mind when making a decision	the act of observing; taking a patient look
formal ceremony about important occasions	conformity with law or custom or practice etc.
a condition that accompanies or influences some event or activity	the act of noticing or paying attention
the set of facts or circumstances that surround a situation or event	a formal event performed on a special occasion