Gaul vs Gallia

Gaul and Gallia both are nouns.

Word	Noun	Adjective	Verb	Adverb
Gaul	Yes	No	No	No
Gallia	Yes	No	No	No

As nouns, Gaul and Gallia are synonyms defined as:

Gaul and Gallia: an ancient region of western Europe that included what is now northern Italy and France and Belgium and part of Germany and the Netherlands

Gaul (noun)	Gallia (noun)
an ancient region of western Europe that included what is now northern Italy and France and Belgium and part of Germany and the Netherlands	an ancient region of western Europe that included what is now northern Italy and France and Belgium and part of Germany and the Netherlands
a Celt of ancient Gaul
a person of French descent