casting vs fly casting

casting and fly casting both are nouns.

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

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

casting: the act of throwing a fishing line out over the water by means of a rod and reel
fly casting: casting an artificial fly as a lure

Other hyponyms of casting include bait casting, overcast, surf casting, surf fishing.

casting (noun)	fly casting (noun)
the act of creating something by casting it in a mold	casting an artificial fly as a lure
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