call waiting vs telephony

call waiting and telephony both are nouns.

Word	Noun	Adjective	Verb	Adverb
call waiting	Yes	No	No	No
telephony	Yes	No	No	No

As nouns, telephony is a hypernym of call waiting; that is, telephony is a word with a broader meaning than call waiting:

call waiting: a way of letting you know that someone else is calling when you are using your telephone
telephony: transmitting speech at a distance

Other hypernyms of call waiting include telephone.

call waiting (noun)	telephony (noun)
a way of letting you know that someone else is calling when you are using your telephone	transmitting speech at a distance