association vs AARP

association and AARP both are nouns.

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

As nouns, AARP is a hyponym of association; that is, AARP is a word with a more specific, narrower meaning than association:

association (noun)	AARP (noun)
the act of consorting with or joining with others	an association of people to promote the welfare of senior citizens
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