Italian vs Oscan

Italian and Oscan both are nouns.

Word	Noun	Adjective	Verb	Adverb
Italian	Yes	Yes	No	No
Oscan	Yes	No	No	No

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

Italian (noun)	Oscan (noun)
the Romance language spoken in Italy	an extinct Italic language of ancient southern Italy, spoken by a number of tribes, including the Samnites, the Aurunci, and the Sidicini
a native or inhabitant of Italy	an Oscan-speaking member of an ancient people of Campania

Italian (adjective)	Oscan (adjective)
of or pertaining to or characteristic of Italy or its people or culture or language