phone vs hold on

phone is a noun but hold on is not a noun.

Word	Noun	Adjective	Verb	Adverb
phone	Yes	No	Yes	No
hold on	No	No	Yes	No

phone (noun)	hold on (noun)
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

phone (verb)	hold on (verb)
get or try to get into communication (with someone) by telephone	be persistent, refuse to stop
	stop and wait, as if awaiting further instructions or developments
	hold the phone line open
	hold firmly
	retain possession of