observance vs function

observance and function both are nouns.

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

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

Other hypernyms of observance include affair, occasion, social affair, social function, social gathering, social occasion.

observance (noun)	function (noun)
the act of observing; taking a patient look	the actions and activities assigned to or required or expected of a person or group
conformity with law or custom or practice etc.	what something is used for
the act of noticing or paying attention	a set sequence of steps, part of larger computer program
a formal event performed on a special occasion	a formal or official social gathering or ceremony of people
	a formal or official social gathering or ceremony
	(mathematics) a mathematical relation such that each element of a given set (the domain of the function) is associated with an element of another set (the range of the function)
	a relation such that one thing is dependent on another

observance (verb)	function (verb)
	perform duties attached to a particular office or place or function
	perform as expected when applied
	serve a purpose, role, or function