sigh vs emit

sigh is a noun but emit is not a noun.

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

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

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

sigh (noun)	emit (noun)
an utterance made by exhaling audibly
a sound like a person sighing

sigh (verb)	emit (verb)
heave or utter a sigh; breathe deeply and heavily	expel (gases or odors)
utter with a sigh	express audibly; utter sounds (not necessarily words)
	give off, send forth, or discharge; as of light, heat, or radiation, vapor, etc.