effort vs overexertion

effort and overexertion both are nouns.

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

As nouns, overexertion is a hyponym of effort; that is, overexertion is a word with a more specific, narrower meaning than effort:

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

effort (noun)	overexertion (noun)
earnest and conscientious activity intended to do or accomplish something	excessive exertion; so much exertion that discomfort or injury results
use of physical or mental energy; hard work
a notable achievement
a series of actions advancing a principle or tending toward a particular end