Spanish language
In Spain and in some other parts of the Spanish-speaking world, Spanish is called not only (Spanish) but also (Castilian), the language from the kingdom of Castile, contrasting it with other languages spoken in Spain such as Galician, Basque, Asturian, Catalan, Aragonese and Occitan.
Language border
For example, Spanish is spoken in most Central American and South American countries, but also in Spain. There are subtle but recognizable differences between the dialects, but there are different dialects even within the country of Spain. In many cultures there are still subtle differences between the terminology (called the register) used when talking to your boss and talking to your mother or talking to your friends. So where are the language borders?