E vs alphabetic character

E and alphabetic character both are nouns.

Word	Noun	Adjective	Verb	Adverb
E	Yes	No	No	No
alphabetic character	Yes	No	No	No

As nouns, alphabetic character is a hypernym of E; that is, alphabetic character is a word with a broader meaning than E:

E: the 5th letter of the Roman alphabet
alphabetic character: the conventional characters of the alphabet used to represent speech

Other hypernyms of E include letter, letter of the alphabet.

E (noun)	alphabetic character (noun)
the 5th letter of the Roman alphabet	the conventional characters of the alphabet used to represent speech
the cardinal compass point that is at 90 degrees
a radioactive transuranic element produced by bombarding plutonium with neutrons
a fat-soluble vitamin that is essential for normal reproduction; an important antioxidant that neutralizes free radicals in the body