telecommunication vs telecom

telecommunication and telecom both are nouns.

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

As nouns, telecommunication and telecom are synonyms defined as:

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

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