sexiness vs sexual desire

sexiness and sexual desire both are nouns.

Word	Noun	Adjective	Verb	Adverb
sexiness	Yes	No	No	No
sexual desire	Yes	No	No	No

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

Other hypernyms of sexiness include concupiscence, eros, physical attraction.

sexiness (noun)	sexual desire (noun)
The state or quality of being sexy, of possessing the traits of sexual appeal.	a desire for sexual intimacy
the arousal of feelings of sexual desire