small capital vs small cap

small capital and small cap both are nouns.

Word	Noun	Adjective	Verb	Adverb
small capital	Yes	No	No	No
small cap	Yes	No	No	No

As nouns, small capital and small cap are synonyms defined as:

small capital and small cap: a character having the form of an upper-case letter but the same height as lower-case letters

small capital (noun)	small cap (noun)
a character having the form of an upper-case letter but the same height as lower-case letters	a character having the form of an upper-case letter but the same height as lower-case letters
	a corporation with a small capitalization