runic letter vs graphic symbol

runic letter and graphic symbol both are nouns.

Word	Noun	Adjective	Verb	Adverb
runic letter	Yes	No	No	No
graphic symbol	Yes	No	No	No

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

runic letter: any character from an ancient Germanic alphabet used in Scandinavia from the 3rd century to the Middle Ages
graphic symbol: a written symbol that is used to represent speech

Other hypernyms of runic letter include character, graph, grapheme.

runic letter (noun)	graphic symbol (noun)
any character from an ancient Germanic alphabet used in Scandinavia from the 3rd century to the Middle Ages	a written symbol that is used to represent speech