runic letter vs rune

runic letter and rune both are nouns.

Word	Noun	Adjective	Verb	Adverb
runic letter	Yes	No	No	No
rune	Yes	No	No	No

As nouns, runic letter and rune are synonyms defined as:

runic letter and rune: any character from an ancient Germanic alphabet used in Scandinavia from the 3rd century to the Middle Ages

runic letter (noun)	rune (noun)
any character from an ancient Germanic alphabet used in Scandinavia from the 3rd century to the Middle Ages	any character from an ancient Germanic alphabet used in Scandinavia from the 3rd century to the Middle Ages