pontoon vs pontoon bridge

pontoon and pontoon bridge both are nouns.

Word	Noun	Adjective	Verb	Adverb
pontoon	Yes	No	No	No
pontoon bridge	Yes	No	No	No

pontoon (noun)	pontoon bridge (noun)
a float supporting a seaplane	a temporary bridge built over a series of pontoons
(nautical) a floating structure (as a flat-bottomed boat) that serves as a dock or to support a bridge