expansion vs step-up

expansion and step-up both are nouns.

Word	Noun	Adjective	Verb	Adverb
expansion	Yes	No	No	No
step-up	Yes	No	No	No

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

expansion: the act of increasing (something) in size or volume or quantity or scope
step-up: the act of increasing something

Other hypernyms of expansion include increase.

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

Other hypernyms of expansion include increase.

expansion (noun)	step-up (noun)
the act of increasing (something) in size or volume or quantity or scope	the act of increasing something
adding information or detail
a discussion that provides additional information
a function expressed as a sum or product of terms