fun vs activity

fun and activity both are nouns.

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

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

fun (noun)	activity (noun)
activities that are enjoyable or amusing	any specific behavior
violent and excited activity	the trait of being active; moving or acting rapidly and energetically
a disposition to find (or make) causes for amusement	an organic process that takes place in the body
verbal wit or mockery (often at another's expense but not to be taken seriously)	a process existing in or produced by nature (rather than by the intent of human beings)
	the state of being active
	(chemistry) the capacity of a substance to take part in a chemical reaction