television vs telly

television and telly both are nouns.

Word	Noun	Adjective	Verb	Adverb
television	Yes	No	No	No
telly	Yes	No	No	No

As nouns, television and telly are synonyms defined as:

television and telly: an electronic device that receives television signals and displays them on a screen

Other synonyms of television include boob tube, goggle box, idiot box, television receiver, television set, tv, tv set.

television (noun)	telly (noun)
a telecommunication system that transmits images of objects (stationary or moving) between distant points	an electronic device that receives television signals and displays them on a screen
an electronic device that receives television signals and displays them on a screen
broadcasting visual images of stationary or moving objects