Names given to the Spanish language
Formally speaking, the national language of Spain, the official Spanish language, is the Castilian language (as opposed to regional Spanish languages like Galician, Catalan, Asturleonese and Basque). As such both names, "español" and "castellano", have distinct and independent meanings that may be required for clarity in some specific contexts.
Generally speaking, though, both terms can be used to refer to the (national) Spanish language as a whole, with a preference for one over the other that depends on the context or the speaker's origin. "Castellano" (as well as "Castilian" in English) has another, more restricted, meaning, relating either to the old Romance language spoken in the Kingdom of Castile in the Middle Ages, predecessor of the modern Spanish language, or to the variety of Spanish nowadays spoken in the historical region of Castile, in central Spain.
Caratachea
Basque (/bæsk/ or /bɑːsk/; Basque: Euskara, IPA: [eus̺ˈkaɾa]) is the language spoken by the Basques. Linguistically, Basque is unrelated to the other languages of Europe and indeed, as a language isolate, to any other known language. The Basques are indigenous to, and primarily inhabit, the Basque Country, a region that straddles the westernmost Pyrenees in adjacent parts of northern Spain and southwestern France. The Basque language is spoken by 27% of Basques in all territories (714,135 out of 2,648,998).[2] Of these, 93% (663,035) are in the Spanish area of the Basque Country and the remaining 7% (51,100) are in the French portion.[2]
Native speakers live in a contiguous area that includes parts of four Spanish territories and the three "ancient provinces" in France. Gipuzkoa, most of Biscay, a few municipalities of Álava, and the northern area of Navarre formed the core of the remaining Basque-speaking area before measures were introduced in the 1980s to strengthen the language. By contrast, most of Álava, the western part of Biscay and central and southern areas of Navarre are predominantly populated by native speakers of Spanish, either because Basque was replaced by Spanish over the centuries, in some areas (most of Álava and central Navarre), or because it was possibly never spoken there, in other areas (Enkarterri and southeastern Navarre).