balloon vs envelope

balloon and envelope both are nouns.

Word	Noun	Adjective	Verb	Adverb
balloon	Yes	No	Yes	No
envelope	Yes	No	No	No

balloon (noun)	envelope (noun)
large tough nonrigid bag filled with gas or heated air	any wrapper or covering
small thin inflatable rubber bag with narrow neck	a flat (usually rectangular) container for a letter, thin package, etc.
	the bag containing the gas in a balloon
	the maximum operating capability of a system (especially an aircraft)
	a natural covering (as by a fluid)
	a curve that is tangent to each of a family of curves

balloon (verb)	envelope (verb)
become inflated
ride in a hot-air balloon