percentage sign vs grapheme

percentage sign and grapheme both are nouns.

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

As nouns, grapheme is a hypernym of percentage sign; that is, grapheme is a word with a broader meaning than percentage sign:

percentage sign: a sign (`%') used to indicate that the number preceding it should be understood as a proportion multiplied by 100
grapheme: a written symbol that is used to represent speech

Other hypernyms of percentage sign include character, graph, graphic symbol.

percentage sign (noun)	grapheme (noun)
a sign (`%') used to indicate that the number preceding it should be understood as a proportion multiplied by 100	a written symbol that is used to represent speech