percent sign vs grapheme

percent sign and grapheme both are nouns.

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

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

percent 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 percent sign include character, graph, graphic symbol.

percent 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