witticism vs fun

witticism and fun both are nouns.

Word	Noun	Adjective	Verb	Adverb
witticism	Yes	No	No	No
fun	Yes	No	No	No

As nouns, fun is a hyponym of witticism; that is, fun is a word with a more specific, narrower meaning than witticism:

witticism: a message whose ingenuity or verbal skill or incongruity has the power to evoke laughter
fun: verbal wit or mockery (often at another's expense but not to be taken seriously)

witticism (noun)	fun (noun)
a message whose ingenuity or verbal skill or incongruity has the power to evoke laughter	activities that are enjoyable or amusing
	violent and excited activity
	a disposition to find (or make) causes for amusement
	verbal wit or mockery (often at another's expense but not to be taken seriously)