fun vs witticism

fun and witticism both are nouns.

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

As nouns, witticism is a hypernym of fun; that is, witticism is a word with a broader meaning than fun:

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

Other hypernyms of fun include humor, humour, wit, wittiness.

fun (noun)	witticism (noun)
activities that are enjoyable or amusing	a message whose ingenuity or verbal skill or incongruity has the power to evoke laughter
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)