Spanish or Castilian (español or castellano in Spanish) is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in the central-north of Iberia during the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the later Medieval period.
Modern Spanish developed with the "Readjustment of the Consonants" (Reajuste de las Sibilantes) that began in 15th century. The language continues to adopt foreign words from a variety of other languages, as well as developing new words. Spanish was taken most notably to the Americas as well as to Africa and Asia Pacific with the expansion of the Spanish Empire between the fifteenth and nineteenth centuries, where it became the most important language for government and trade.
In 1999, there were 358 million people speaking Spanish as a native language and a total of 417 million speakers worldwide. Currently these figures are up to 400 and 500 million people respectively. Spanish is the second most natively spoken language in the world, after Mandarin Chinese. Mexico contains the largest population of Spanish speakers. Spanish is one of the six official languages of the United Nations.
There are important variations spoken among the regions of Spain and throughout Spanish-speaking America. One major phonological difference between Castilian, broadly speaking, the accents spoken in most of Spain, and the accent of much of southern Spain, the Canary Islands and all the Latin American accents of Spanish, is the absence of a voiceless dental fricative as in English thing) in the latter. In Spain, the Castilian accent is commonly regarded as the standard variety used on radio and television, although attitudes towards southern accents have changed significantly in the last 50 years. In addition to variations in pronunciation, minor lexical and grammatical differences exist. For example, loísmo is the use of slightly different pronouns and differs from the standard.
The variety with the most speakers is Mexican Spanish. It is spoken by more than the twenty percent of the Spanish speakers (107 million of the total 494 million, according to the table above). One of its main features is the reduction or loss of the unstressed vowels, mainly when they are in contact with the sound /s/.
