percent sign vs percentage sign

percent sign and percentage sign both are nouns.

Word	Noun	Adjective	Verb	Adverb
percent sign	Yes	No	No	No
percentage sign	Yes	No	No	No

As nouns, percent sign and percentage sign are synonyms defined as:

percent sign and percentage sign: a sign (`%') used to indicate that the number preceding it should be understood as a proportion multiplied by 100

percent sign (noun)	percentage sign (noun)
a sign (`%') used to indicate that the number preceding it should be understood as a proportion multiplied by 100	a sign (`%') used to indicate that the number preceding it should be understood as a proportion multiplied by 100