float vs pontoon

float and pontoon both are nouns.

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

As nouns, pontoon is a hyponym of float; that is, pontoon is a word with a more specific, narrower meaning than float:

Other hyponyms of float include bob, bobber, bobfloat, cork, chip, flotation device, life preserver, preserver, raft.

float (noun)	pontoon (noun)
an air-filled sac near the spinal column in many fishes that helps maintain buoyancy	a float supporting a seaplane
something that floats on the surface of water	(nautical) a floating structure (as a flat-bottomed boat) that serves as a dock or to support a bridge
a hand tool with a flat face used for smoothing and finishing the surface of plaster or cement or stucco
an elaborate display mounted on a platform carried by a truck (or pulled by a truck) in a procession or parade
a drink with ice cream floating in it
the number of shares outstanding and available for trading by the public
the time interval between the deposit of a check in a bank and its payment

float (verb)	pontoon (verb)
convert from a fixed point notation to a floating point notation
allow (currencies) to fluctuate
make the surface of level or smooth
put into the water
be in motion due to some air or water current
be afloat either on or below a liquid surface and not sink to the bottom
set afloat
move lightly, as if suspended
circulate or discuss tentatively; test the waters with