Castilian

In the past, North Castilian used to be considered, by the Spanish Royal Academy, the "model" or "yardstick" for the Spanish spoken in the two dozen or so Spanish-speaking countries. North Castilian, however, preserves the distinction between the two phonemes /s/ (alveolar sibilant, written s) and /T/ (interdental fricative written z or ce,ci) (e.g. casa=house vs. cereza=sherry), that is not used elsewhere since the 16th century.

Castilian is not to be confused with ceceo or seseo. The term seseo is used for the Spanish of the Americas, Canary Islands, and some Andalusian Spanish variants that mixed /s/ and /T/ into /s/, while the term ceceo is used for the other Andalusian Spanish variants that mixed /s/ and /T/ into /T/.

While many Spaniards generally refer to their language as español, in Mexico, Central and South America the language (however pronounced) is often called castellano (Castilian) because the word español is used for "Spaniard". And then in Spain, most Spaniards whose native tongue is not Spanish (about 1 of every 5) call Spanish castellano as well.