groan vs emit

groan is a noun but emit is not a noun.

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

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

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

groan (noun)	emit (noun)
an utterance expressing pain or disapproval

groan (verb)	emit (verb)
indicate pain, discomfort, or displeasure	expel (gases or odors)
	express audibly; utter sounds (not necessarily words)
	give off, send forth, or discharge; as of light, heat, or radiation, vapor, etc.