inhuman treatment vs abuse

inhuman treatment and abuse both are nouns.

Word	Noun	Adjective	Verb	Adverb
inhuman treatment	Yes	No	No	No
abuse	Yes	No	Yes	No

As nouns, abuse is a hypernym of inhuman treatment; that is, abuse is a word with a broader meaning than inhuman treatment:

inhuman treatment: a cruel act; a deliberate infliction of pain and suffering
abuse: cruel or inhumane treatment

Other hypernyms of inhuman treatment include ill-treatment, ill-usage, maltreatment.

inhuman treatment (noun)	abuse (noun)
a cruel act; a deliberate infliction of pain and suffering	improper or excessive use
	cruel or inhumane treatment
	a rude expression intended to offend or hurt

inhuman treatment (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