contraction vs step-down

contraction and step-down both are nouns.

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

As nouns, step-down is a hypernym of contraction; that is, step-down is a word with a broader meaning than contraction:

contraction: the act of decreasing (something) in size or volume or quantity or scope
step-down: the act of decreasing or reducing something

Other hypernyms of contraction include decrease, diminution, reduction.

contraction (noun)	step-down (noun)
the act of decreasing (something) in size or volume or quantity or scope	the act of decreasing or reducing something
(physiology) a shortening or tensing of a part or organ (especially of a muscle or muscle fiber)
a word formed from two or more words by omitting or combining some sounds
the process or result of becoming smaller or pressed together