anus vs asshole

anus and asshole both are nouns.

Word	Noun	Adjective	Verb	Adverb
anus	Yes	No	No	No
asshole	Yes	No	No	No

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

Other hyponyms of anus include arse, arsehole, bunghole, imperforate anus.

anus (noun)	asshole (noun)
the excretory opening at the end of the alimentary canal	vulgar slang for anus
	insulting terms of address for people who are stupid or irritating or ridiculous