affiliation vs association

affiliation and association both are nouns.

Word	Noun	Adjective	Verb	Adverb
affiliation	Yes	No	No	No
association	Yes	No	No	No

As nouns, association is a hypernym of affiliation; that is, association is a word with a broader meaning than affiliation:

As nouns, affiliation and association are synonyms defined as:

Other synonyms of affiliation include tie-up, tie.

affiliation (noun)	association (noun)
the act of becoming formally connected or joined	the act of consorting with or joining with others
a social or business relationship	the process of bringing ideas or events together in memory or imagination
	a formal organization of people or groups of people
	(ecology) a group of organisms (plants and animals) that live together in a certain geographical region and constitute a community with a few dominant species
	(chemistry) any process of combination (especially in solution) that depends on relatively weak chemical bonding
	a relation resulting from interaction or dependence
	a social or business relationship
	the state of being connected together as in memory or imagination