telephony vs telecommunication

telephony and telecommunication both are nouns.

Word	Noun	Adjective	Verb	Adverb
telephony	Yes	No	No	No
telecommunication	Yes	No	No	No

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

telephony: transmitting speech at a distance
telecommunication: (often plural) systems used in transmitting messages over a distance electronically

Other hypernyms of telephony include telecom.

telephony (noun)	telecommunication (noun)
transmitting speech at a distance	(often plural) the branch of electrical engineering concerned with the technology of electronic communication at a distance
	(often plural) systems used in transmitting messages over a distance electronically