scale down vs decrease

scale down is not a noun while decrease is a noun.

Word	Noun	Adjective	Verb	Adverb
scale down	No	No	Yes	No
decrease	Yes	No	Yes	No

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

scale down (verb)	decrease (verb)
reduce proportionally	decrease in size, extent, or range
make smaller	make become smaller