frolicsomeness vs fun

frolicsomeness and fun both are nouns.

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

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

Other hypernyms of frolicsomeness include playfulness.

frolicsomeness (noun)	fun (noun)
lively high-spirited playfulness	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)