decrease vs step-down

decrease and step-down both are nouns.

Word	Noun	Adjective	Verb	Adverb
decrease	Yes	No	Yes	No
step-down	Yes	No	No	No

As nouns, decrease and step-down are synonyms defined as:

Other synonyms of decrease include diminution, reduction.

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

decrease (verb)	step-down (verb)
decrease in size, extent, or range
make become smaller