As an aside, here's a breakdown of who speaks Catalan vs Spanish, in Catalonia, as of 2018:
https://www.idescat.cat/novetats/?id=3446&lang=en
The quick version, in a single image, with the lightest area being the region of Barcelona:
https://www.idescat.cat/novetats/?id=3446&lang=en
The quick version, in a single image, with the lightest area being the region of Barcelona:
Castilian Spanish, when used in English, is often used to denote the dialects spoken in Spain, as opposed to the dialects spoken in Latin America. This is not the topic at hand here, so there isn't much point in calling it Castilian (especially since many English speakers would not be familiar with that term) over Spanish.
adjective
relating to Spain, its people, or its language.
1. the people of Spain.
2. a Romance language spoken in Spain and in much of Central and South America.