erotism vs sexual arousal

erotism and sexual arousal both are nouns.

Word	Noun	Adjective	Verb	Adverb
erotism	Yes	No	No	No
sexual arousal	Yes	No	No	No

As nouns, sexual arousal is a hypernym of erotism; that is, sexual arousal is a word with a broader meaning than erotism:

erotism: a state of anticipation of sexuality
sexual arousal: the arousal of sexual desires in preparation for sexual behavior

erotism (noun)	sexual arousal (noun)
the arousal of feelings of sexual desire	the arousal of sexual desires in preparation for sexual behavior
a state of anticipation of sexuality