siglum vs graphic symbol

siglum and graphic symbol both are nouns.

Word	Noun	Adjective	Verb	Adverb
siglum	Yes	No	No	No
graphic symbol	Yes	No	No	No

As nouns, graphic symbol is a hypernym of siglum; that is, graphic symbol is a word with a broader meaning than siglum:

siglum: a sign, abbreviation, letter, or character standing for words in ancient manuscripts or on coins or medals.
graphic symbol: a written symbol that is used to represent speech

Other hypernyms of siglum include character, graph, grapheme.

siglum (noun)	graphic symbol (noun)
a sign, abbreviation, letter, or character standing for words in ancient manuscripts or on coins or medals.	a written symbol that is used to represent speech