mistreatment vs abuse

mistreatment and abuse both are nouns.

Word	Noun	Adjective	Verb	Adverb
mistreatment	Yes	No	No	No
abuse	Yes	No	Yes	No

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

mistreatment (noun)	abuse (noun)
the practice of treating (someone or something) badly	improper or excessive use
	cruel or inhumane treatment
	a rude expression intended to offend or hurt

mistreatment (verb)	abuse (verb)
	change the inherent purpose or function of something
	use wrongly or improperly or excessively
	use foul or abusive language towards
	treat badly