In English, Castilian Spanish usually refers to the variety of European Spanish spoken in northern and central Spain or as the language standard for radio and TV speakers. In Spanish, the term castellano (Castilian) may refer to the Spanish language as a whole, to the dialects spoken in central and northern Spain, or to the medieval language which was a predecessor to modern Spanish.

Spanish (, ), also called Castilian (, ), is a Romance language that originated in the Castile region of Spain and today has hundreds of millions of native-speakers across the world.