small cap vs small capital

small cap and small capital both are nouns.

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

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

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

small cap (noun)	small capital (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