Greek alphabet vs alphabet

Greek alphabet and alphabet both are nouns.

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

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

Greek alphabet: the alphabet used by ancient Greeks
alphabet: a character set that includes letters and is used to write a language

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

Greek alphabet (noun)	alphabet (noun)
the alphabet used by ancient Greeks	the elementary stages of any subject (usually plural)
	a character set that includes letters and is used to write a language