necking vs arousal

necking and arousal both are nouns.

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

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

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

Other hypernyms of necking include foreplay, stimulation.

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