In Spain and in some other parts of the Spanish-speaking world, Spanish is called not only (Spanish) but also (Castilian), the language of the region of Castile, contrasting it with other languages spoken in Spain such as Galician, Basque and Catalan.
The Diccionario panhispánico de dudas (a language guide published by the Spanish Royal Academy) states that, although the Spanish Royal Academy prefers to use the term español in its publications when referring to the Spanish language, both terms-español and castellano-are regarded as synonymous and equally valid [REF].