heterosexuality vs heterosexualism

heterosexuality and heterosexualism both are nouns.

Word	Noun	Adjective	Verb	Adverb
heterosexuality	Yes	No	No	No
heterosexualism	Yes	No	No	No

As nouns, heterosexuality and heterosexualism are synonyms defined as:

heterosexuality and heterosexualism: a sexual attraction to (or sexual relations with) persons of the opposite sex

Other synonyms of heterosexuality include straightness.

heterosexuality (noun)	heterosexualism (noun)
a sexual attraction to (or sexual relations with) persons of the opposite sex	a sexual attraction to (or sexual relations with) persons of the opposite sex