word play vs caper

word play and caper both are nouns.

Word	Noun	Adjective	Verb	Adverb
word play	Yes	No	No	No
caper	Yes	No	Yes	No

As nouns, caper is a hypernym of word play; that is, caper is a word with a broader meaning than word play:

word play: playing on words or speech sounds
caper: gay or light-hearted recreational activity for diversion or amusement

Other hypernyms of word play include frolic, gambol, play, romp.

word play (noun)	caper (noun)
playing on words or speech sounds	gay or light-hearted recreational activity for diversion or amusement
	a crime (especially a robbery)
	a ludicrous or grotesque act done for fun and amusement
	a playful leap or hop
	pickled flower buds used as a pungent relish in various dishes and sauces
	any of numerous plants of the genus Capparis

word play (verb)	caper (verb)
	jump about playfully