dwindling vs decrease

dwindling and decrease both are nouns.

Word	Noun	Adjective	Verb	Adverb
dwindling	Yes	Yes	No	No
decrease	Yes	No	Yes	No

As nouns, decrease is a hypernym of dwindling; that is, decrease is a word with a broader meaning than dwindling:

Other hypernyms of dwindling include drop-off, lessening.

dwindling (noun)	decrease (noun)
a becoming gradually less	the act of decreasing or reducing something
	the amount by which something decreases
	a change downward
	a process of becoming smaller or shorter

dwindling (adjective)	decrease (adjective)
gradually decreasing until little remains

dwindling (verb)	decrease (verb)
	decrease in size, extent, or range
	make become smaller