Spanish or Castilian (español or castellano in Spanish) is a Romance language in the Ibero-Romance group that evolved from several dialects and languages in the northern fringes of the Iberian Peninsula during the 10th century and gradually spread through the Kingdom of Castile, becoming the foremost language for government and trade in the Spanish Empire.
Latin, the basis of all Romance languages including Spanish, was introduced to the Iberian Peninsula by the Romans during the Second Punic War around 210 BC. 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. Castilian 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.
As of 2010, 329 to 358 million people speak Spanish as a native language and a total of 417 million people speak it worldwide. It 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.