Castilian
Castilian is the historical name of the Spanish language, which originated in the old Spanish kingdom of Castile. In Spanish, castellano has the same meaning as espaÃÂñol (Spanish), being preferred in Spain, since there are more languages in Spain than Spanish itself. In English, Castilian refers to the dialect spoken in the ancient kingdom of Castile - roughly, Castilla y LÃÂéon or, generally, to the Spanish language as spoken in Spain.
In the past, the North Castilian standard, as fixed by the Spanish Royal Academy, was considered the "model" or "yardstick" for the Spanish spoken in the two dozen or so Spanish-speaking countries. Nowadays, the Spanish Royal Academy works with in association with other countries language academies to set the standards of the language.
Castilian preserves the distinction between the two phonemes currently expressed as /s/ (alveolar sibilant, written s) and /T/ (interdental fricative written z or c(e), c(i)) (e.g. casa=house vs. caza=hunting), a distinction that has not been observed elsewhere since the 16th century.
Seseo and ceceo (despite the incorrect use sometimes made of the latter term to describe Castilian pronunciation itself) refer to two phenomena in other varieties of Spanish in which the Castilian distinction between /s/ and /T/ is not observed. Seseo, which is a major feature of the Spanish of the Americas, the Canary Islands, and some varieties of Andalusian Spanish, consists in realizing Castilian /T/ as /s/, while the term ceceo is used for the reverse phenomenon, to be found in some other Andalusian Spanish variants, of pronouncing Castilian /s/ as /T/.