moan vs groan

moan and groan both are nouns.

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

As nouns, moan and groan are synonyms defined as:

As verbs, moan and groan are synonyms defined as:

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

moan (verb)	groan (verb)
indicate pain, discomfort, or displeasure	indicate pain, discomfort, or displeasure