epsilon vs alphabetic character

epsilon and alphabetic character both are nouns.

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

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

epsilon: the 5th letter of the Greek alphabet
alphabetic character: the conventional characters of the alphabet used to represent speech

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

epsilon (noun)	alphabetic character (noun)
the 5th letter of the Greek alphabet	the conventional characters of the alphabet used to represent speech