fishing vs casting

fishing and casting both are nouns.

Word	Noun	Adjective	Verb	Adverb
fishing	Yes	No	No	No
casting	Yes	No	No	No

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

fishing: the act of someone who fishes as a diversion
casting: the act of throwing a fishing line out over the water by means of a rod and reel

Other hyponyms of fishing include angling, cast.

fishing (noun)	casting (noun)
the act of someone who fishes as a diversion	the act of creating something by casting it in a mold
the occupation of catching fish for a living	the act of throwing a fishing line out over the water by means of a rod and reel
	the choice of actors to play particular roles in a play or movie
	object formed by a mold