Actually, people moved by "political reasons" call
it both "castellano" and "español", depending on "what political reasons" they
are impelled by.
When Catalans speak about "castellà", for
instance, they are saying "my language is a Spanish language too, and in my
opinion, Spain discriminates those Spanish languages different from the
Castilian one. I want it to change", it is, they want to be a part of Spain, but
not like now (almost a mere province).
When they speak about "espanyol", they are saying:
"Yep, Spain's language is Spanish, of course. As MY language is Catalan, I'm not
Spanish", it is, they feel like not being a province of Spain/Castille
anymore.
Non politised people use the non marked term, which
is "castellà".
Anyway, lately Spanish nationalists are recovering
the use of "español", meaning: "the language of every Spanish". Bad
move...
Cheers.
Efectively in Catalonia, Galicia and Basque
Country some person by political reason use the term "castellano", but also
non-politiced persons in these areas use the term "español". In English
linguistic writting the term Spanish is more common, and the term Castilian is
used in the sense of "Old Spanish". But for native speakers of most areas
"castellano" or "español" is equally acceptable and none of them is a marked
term.
Davius S.