coo vs emit

coo is a noun but emit is not a noun.

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

As verbs, emit is a hypernym of coo; that is, emit is a word with a broader meaning than coo:

Other hypernyms of coo include let loose, let out, utter.

coo (noun)	emit (noun)
the sound made by a pigeon

coo (verb)	emit (verb)
cry softly, as of pigeons	expel (gases or odors)
speak softly or lovingly	express audibly; utter sounds (not necessarily words)
	give off, send forth, or discharge; as of light, heat, or radiation, vapor, etc.