Peninsular Spanish (Spanish: español peninsular), also known as Spanish of Spain (Spanish: español de España) European Spanish (Spanish: español europeo) and Iberian Spanish (Spanish: español ibérico), sometimes inaccurately referred to as Castilian Spanish (Spanish: español castellano) refers to the varieties of the Spanish language spoken in the Iberian Peninsula, as opposed to the Spanish spoken in the Americas and in the Canary Islands. The related term Castilian Spanish is often applied to formal varieties of Spanish as spoken in Spain. According to folk tradition, the "purest" form of Peninsular Spanish is spoken in the Castilian province of Valladolid, although the concept of "pure" language has been questioned by modern linguists.
In phonology, the most prominent distinguishing element of Peninsular Spanish varieties, except for the southernmost ones, is the preservation of a distinction between the phonemes and , represented respectively with the letters ?s? on one hand and ?z?, or ?c? before ?e / i?, on the other. This is usually called distinción in Spanish, while the lack of distinction between the two is called seseo or ceceo, depending on the phonetic outcome ( in the former case, in the latter). On one hand, in the Spanish of the Americas and in parts of southern Spain, words spelled with ?z?, with ?c? before ?e? or ?i?, or with ?s? are all typically pronounced with a sound similar to the English /s/; on the other hand, in the Peninsular dialects with distinción, words with ?z? or with ?c? before ?e? or ?i? are pronounced with --that is, the initial sound of the English word think. However, many Andalusian dialects and the Spanish spoken in the Canary Islands do not use distinción as a general rule, but rather use either seseo or ceceo.
In morphology, the most notable distinguishing feature of Peninsular Spanish is the use of the pronoun vosotros (along with its oblique form os) and its corresponding verb forms for the second person plural familiar. In virtually all other varieties of Modern Spanish, for the second person plural, the familiar and the formal are merged in ustedes, with its verb forms. Again, the use of vosotros is uncommon in the Canary Islands and only partially introduced in Western Andalusia.