Greek alphabet vs ABCs

Greek alphabet and ABCs both are nouns.

Word	Noun	Adjective	Verb	Adverb
Greek alphabet	Yes	No	No	No
ABCs	Yes	No	No	No

As nouns, ABCs is a hypernym of Greek alphabet; that is, ABCs is a word with a broader meaning than Greek alphabet:

Other hypernyms of Greek alphabet include ABC's, ABC, alphabet.

Greek alphabet (noun)	ABCs (noun)
the alphabet used by ancient Greeks	a character set that includes letters and is used to write a language