flue vs chimneystack

flue and chimneystack both are nouns.

Word	Noun	Adjective	Verb	Adverb
flue	Yes	No	No	No
chimneystack	Yes	No	No	No

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

flue: a conduit to carry off smoke
chimneystack: the part of the chimney that is above the roof; usually has several flues

Other hyponyms of flue include chimney, chimney, lamp chimney.

flue (noun)	chimneystack (noun)
a conduit to carry off smoke	the part of the chimney that is above the roof; usually has several flues
organ pipe whose tone is produced by air passing across the sharp edge of a fissure or lip
flat bladelike projection on the arm of an anchor