croak vs emit

croak is a noun but emit is not a noun.

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

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

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

croak (noun)	emit (noun)
a harsh hoarse utterance (as of a frog)

croak (verb)	emit (verb)
pass from physical life and lose all bodily attributes and functions necessary to sustain life	expel (gases or odors)
make complaining remarks or noises under one's breath	express audibly; utter sounds (not necessarily words)
utter a hoarse sound, like a raven	give off, send forth, or discharge; as of light, heat, or radiation, vapor, etc.