alphabetic character vs letter of the alphabet

alphabetic character and letter of the alphabet both are nouns.

Word	Noun	Adjective	Verb	Adverb
alphabetic character	Yes	No	No	No
letter of the alphabet	Yes	No	No	No

As nouns, alphabetic character and letter of the alphabet are synonyms defined as:

alphabetic character and letter of the alphabet: the conventional characters of the alphabet used to represent speech

Other synonyms of alphabetic character include letter.

alphabetic character (noun)	letter of the alphabet (noun)
the conventional characters of the alphabet used to represent speech	the conventional characters of the alphabet used to represent speech