petting vs arousal

petting and arousal both are nouns.

Word	Noun	Adjective	Verb	Adverb
petting	Yes	No	No	No
arousal	Yes	No	No	No

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

petting: affectionate play (or foreplay without contact with the genital organs)
arousal: mutual sexual fondling prior to sexual intercourse

Other hypernyms of petting include foreplay, stimulation.

petting (noun)	arousal (noun)
affectionate play (or foreplay without contact with the genital organs)	the act of arousing
	mutual sexual fondling prior to sexual intercourse
	awakening from sleep
	a state of heightened physiological activity