shortening vs step-down

shortening and step-down both are nouns.

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

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

Other hypernyms of shortening include decrease, diminution, reduction.

shortening (noun)	step-down (noun)
act of decreasing in length	the act of decreasing or reducing something
fat such as butter or lard used in baked goods