Castilian vs Castilian language

Castilian and Castilian language both are nouns.

Word	Noun	Adjective	Verb	Adverb
Castilian	Yes	No	No	No
Castilian language	Yes	No	No	No

As nouns, Castilian and Castilian language are synonyms defined as:

Castilian and Castilian language: the Spanish language as spoken in Castile

Castilian (noun)	Castilian language (noun)
the Spanish language as spoken in Castile	the Spanish language as spoken in Castile
a native or inhabitant of Castile