overexertion vs exertion

overexertion and exertion both are nouns.

Word	Noun	Adjective	Verb	Adverb
overexertion	Yes	No	No	No
exertion	Yes	No	No	No

As nouns, exertion is a hypernym of overexertion; that is, exertion is a word with a broader meaning than overexertion:

overexertion: excessive exertion; so much exertion that discomfort or injury results
exertion: use of physical or mental energy; hard work

Other hypernyms of overexertion include effort, elbow grease, sweat, travail.

overexertion (noun)	exertion (noun)
excessive exertion; so much exertion that discomfort or injury results	use of physical or mental energy; hard work