joke vs fool

joke and fool both are nouns.

Word	Noun	Adjective	Verb	Adverb
joke	Yes	No	Yes	No
fool	Yes	No	Yes	No

As verbs, fool is a hyponym of joke; that is, fool is a word with a more specific, narrower meaning than joke:

Other hyponyms of joke include gag, quip, arse around, fool around, horse around, pun.

joke (noun)	fool (noun)
a ludicrous or grotesque act done for fun and amusement	a person who lacks good judgment
activity characterized by good humor	a person who is gullible and easy to take advantage of
a triviality not to be taken seriously	a professional clown employed to entertain a king or nobleman in the Middle Ages
a humorous anecdote or remark intended to provoke laughter

joke (verb)	fool (verb)
act in a funny or teasing way	indulge in horseplay
tell a joke; speak humorously	fool or hoax
	spend frivolously and unwisely
	make a fool or dupe of