air-intake vs duct

air-intake and duct both are nouns.

Word	Noun	Adjective	Verb	Adverb
air-intake	Yes	No	No	No
duct	Yes	No	No	No

As nouns, duct is a hypernym of air-intake; that is, duct is a word with a broader meaning than air-intake:

air-intake (noun)	duct (noun)
a duct that admits air to be mixed with fuel	an enclosed conduit for a fluid
	a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance
	a continuous tube formed by a row of elongated cells lacking intervening end walls