Egyptian vs Theban

Egyptian and Theban both are nouns.

Word	Noun	Adjective	Verb	Adverb
Egyptian	Yes	Yes	No	No
Theban	Yes	Yes	No	No

As nouns, Theban is a hyponym of Egyptian; that is, Theban is a word with a more specific, narrower meaning than Egyptian:

Other hyponyms of Egyptian include Copt, Cairene, Nubian.

Egyptian (noun)	Theban (noun)
the ancient and now extinct language of Egypt under the Pharaohs; written records date back to 3000 BC	a Greek inhabitant of ancient Thebes
a native or inhabitant of Egypt	an Egyptian inhabitant of ancient Thebes

Egyptian (adjective)	Theban (adjective)
of or relating to or characteristic of Egypt or its people or their language	of or relating to the Greek city of Thebes or its people or culture
	of or relating to the Egyptian city of Thebes or its people or culture