decrease vs drop-off

decrease and drop-off both are nouns.

Word	Noun	Adjective	Verb	Adverb
decrease	Yes	No	Yes	No
drop-off	Yes	No	No	No

As nouns, decrease and drop-off are synonyms defined as:

Other synonyms of decrease include lessening.

decrease (noun)	drop-off (noun)
the act of decreasing or reducing something	a change downward
the amount by which something decreases	a steep high face of rock
a change downward	a noticeable deterioration in performance or quality
a process of becoming smaller or shorter

decrease (verb)	drop-off (verb)
decrease in size, extent, or range
make become smaller