Spanish people tend to call this language español when contrasting it with languages of other states (e.g., in a list with French and English), but call it castellano (Castilian, from the Castile region) when contrasting it with other languages of Spain (such as Galician, Basque, and Catalan/Valencian). In this manner, the Spanish Constitution of 1978 uses the term castellano to define the official language of the whole State.
Spanish is one of the official languages of the United Nations and the European Union. The majority of its speakers are confined to the Western Hemisphere, and Spain.
With approximately 106 million first-language and second-language speakers, Mexico boasts the largest population of Spanish-speakers in the world. The four next largest populations reside in Colombia (45 million), Spain (43 million), Argentina (39 million) and the United States of America (U.S. residents age 5 and older who speak Spanish at home number 31 million).
Spanish is the official and most important language in 22 countries: Argentina, Bolivia (co-official Quechua and Aymara), Chile, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, Equatorial Guinea (co-official French), Guatemala, Honduras, Mexico, Nicaragua, Panama, Paraguay (co-official Guaraní), Peru (co-official Quechua and Aymara), Puerto Rico (co-official English), Spain (co-official in some regions with Catalan, Galician and Basque), Uruguay, Venezuela, and Western Sahara (co-official Arabic).