cable television vs TV

cable television and TV both are nouns.

Word	Noun	Adjective	Verb	Adverb
cable television	Yes	No	No	No
TV	Yes	No	No	No

As nouns, TV is a hypernym of cable television; that is, TV is a word with a broader meaning than cable television:

cable television: television that is transmitted over cable directly to the receiver
TV: broadcasting visual images of stationary or moving objects

Other hypernyms of cable television include telecasting, television, video.

cable television (noun)	TV (noun)
a television system that transmits over cables	broadcasting visual images of stationary or moving objects
television that is transmitted over cable directly to the receiver