bastion vs acropolis

bastion and acropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
bastion	Yes	No	No	No
acropolis	Yes	No	No	No

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

bastion: a stronghold into which people could go for shelter during a battle
acropolis: the citadel in ancient Greek towns

Other hyponyms of bastion include kremlin.

bastion (noun)	acropolis (noun)
projecting part of a rampart or other fortification	the citadel in ancient Greek towns
a stronghold into which people could go for shelter during a battle
a group that defends a principle