chimney vs smokestack

chimney and smokestack both are nouns.

Word	Noun	Adjective	Verb	Adverb
chimney	Yes	No	No	No
smokestack	Yes	No	No	No

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

chimney: a vertical flue that provides a path through which smoke from a fire is carried away through the wall or roof of a building
smokestack: a large tall chimney through which combustion gases and smoke can be evacuated

Other hyponyms of chimney include stack, stovepipe.

chimney (noun)	smokestack (noun)
a vertical flue that provides a path through which smoke from a fire is carried away through the wall or roof of a building	a large tall chimney through which combustion gases and smoke can be evacuated
a glass flue surrounding the wick of an oil lamp