lesbianism vs homosexualism

lesbianism and homosexualism both are nouns.

Word	Noun	Adjective	Verb	Adverb
lesbianism	Yes	No	No	No
homosexualism	Yes	No	No	No

As nouns, homosexualism is a hypernym of lesbianism; that is, homosexualism is a word with a broader meaning than lesbianism:

lesbianism: female homosexuality
homosexualism: a sexual attraction to (or sexual relations with) persons of the same sex

Other hypernyms of lesbianism include gayness, homoeroticism, homosexuality, queerness.

lesbianism (noun)	homosexualism (noun)
female homosexuality	a sexual attraction to (or sexual relations with) persons of the same sex