exhaust vs emit

exhaust is a noun but emit is not a noun.

Word	Noun	Adjective	Verb	Adverb
exhaust	Yes	No	Yes	No
emit	No	No	Yes	No

As verbs, emit is a hyponym of exhaust; that is, emit is a word with a more specific, narrower meaning than exhaust:

exhaust (noun)	emit (noun)
system consisting of the parts of an engine through which burned gases or steam are discharged
gases ejected from an engine as waste products

exhaust (verb)	emit (verb)
wear out completely	expel (gases or odors)
eliminate (a substance)	express audibly; utter sounds (not necessarily words)
use up the whole supply of	give off, send forth, or discharge; as of light, heat, or radiation, vapor, etc.
use up (resources or materials)
deplete