onanism vs self-abuse

onanism and self-abuse both are nouns.

Word	Noun	Adjective	Verb	Adverb
onanism	Yes	No	No	No
self-abuse	Yes	No	No	No

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

onanism: manual stimulation of the genital organs (of yourself or another) for sexual pleasure
self-abuse: manual stimulation of your own genital organ for sexual pleasure

Other hyponyms of onanism include self-stimulation, frottage, hand job, jacking off, jerking off, wank.

onanism (noun)	self-abuse (noun)
manual stimulation of the genital organs (of yourself or another) for sexual pleasure	manual stimulation of your own genital organ for sexual pleasure
a method of birth control in which coitus is initiated but the penis is deliberately withdrawn before ejaculation