Flemish vs ethnos

Flemish and ethnos both are nouns.

Word	Noun	Adjective	Verb	Adverb
Flemish	Yes	Yes	No	No
ethnos	Yes	No	No	No

As nouns, ethnos is a hypernym of Flemish; that is, ethnos is a word with a broader meaning than Flemish:

Flemish: an ethnic group speaking Flemish and living in northern and western Belgium
ethnos: people of the same race or nationality who share a distinctive culture

Other hypernyms of Flemish include ethnic group.

Flemish (noun)	ethnos (noun)
one of two official languages of Belgium; closely related to Dutch	people of the same race or nationality who share a distinctive culture
an ethnic group speaking Flemish and living in northern and western Belgium

Flemish (adjective)	ethnos (adjective)
of or relating to Flanders or its people or language or culture