jet plane vs twinjet

jet plane and twinjet both are nouns.

Word	Noun	Adjective	Verb	Adverb
jet plane	Yes	No	No	No
twinjet	Yes	No	No	No

As nouns, twinjet is a hyponym of jet plane; that is, twinjet is a word with a more specific, narrower meaning than jet plane:

Other hyponyms of jet plane include fan-jet, fanjet, turbofan, turbojet, jetliner, jumbo jet, jumbojet.

jet plane (noun)	twinjet (noun)
an airplane powered by one or more jet engines	a jet plane propelled by two jet engines