foreplay vs sex

foreplay and sex both are nouns.

Word	Noun	Adjective	Verb	Adverb
foreplay	Yes	No	No	No
sex	Yes	No	Yes	No

As nouns, sex is a hypernym of foreplay; that is, sex is a word with a broader meaning than foreplay:

Other hypernyms of foreplay include sex activity, sexual activity, sexual practice.

foreplay (noun)	sex (noun)
mutual sexual fondling prior to sexual intercourse	activities associated with sexual intercourse
	the properties that distinguish organisms on the basis of their reproductive roles
	all of the feelings resulting from the urge to gratify sexual impulses
	either of the two categories (male or female) into which most organisms are divided

foreplay (verb)	sex (verb)
	tell the sex (of young chickens)
	to evoke sexual feelings