pub vs alehouse

pub and alehouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
pub	Yes	No	No	No
alehouse	Yes	No	No	No

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

pub: tavern consisting of a building with a bar and public rooms; often provides light meals
alehouse: a tavern where ale is sold

Other hyponyms of pub include free house.

pub (noun)	alehouse (noun)
tavern consisting of a building with a bar and public rooms; often provides light meals	a tavern where ale is sold