telecom vs telecommunication

telecom and telecommunication both are nouns.

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

As nouns, telecom and telecommunication are synonyms defined as:

telecom and telecommunication: (often plural) systems used in transmitting messages over a distance electronically

telecom (noun)	telecommunication (noun)
(often plural) systems used in transmitting messages over a distance electronically	(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