telephone system vs phone

telephone system and phone both are nouns.

Word	Noun	Adjective	Verb	Adverb
telephone system	Yes	No	No	No
phone	Yes	No	Yes	No

telephone system (noun)	phone (noun)
a communication system that transmits sound between distant points	electronic equipment that converts sound into electrical signals that can be transmitted over distances and then converts received signals back into sounds
	electro-acoustic transducer for converting electric signals into sounds; it is held over or inserted into the ear
	(phonetics) an individual sound unit of speech without concern as to whether or not it is a phoneme of some language

telephone system (verb)	phone (verb)
	get or try to get into communication (with someone) by telephone