The Andalusian (also called andaluz) of dialect Spanish is spoken in Andalusia , Gibraltar , Melilla , Ceuta and parts of southern Extremadura . Andalusian Spanish differs significantly in many respects from northern dialects of Spanish and Standard Spanish , which is largely based on written Spanish and phonetically closer to the northern dialects. Due to the large population of Andalusia, the Andalusian dialect is the second most spoken dialect in Spain , after the transitional variants between Castilian and Andalusian (for example the one from Madrid). Due to massive emigration from Andalusia to the Spanish colonies in the Americas and elsewhere, many American Spanish dialects share some fundamental characteristics with Andalusian Spanish, such as the use of ustedes instead of vosotros for the second person plural, and the widespread use of seseo . Canarian Spanish , Caribbean Spanish , Chilean Spanish and Rioplatense are based on Andalusian.

Sometimes, Andalusian is considered as a dialect.  Many consider it is just a particular way of speaking into the Spanish language .

Andalusian, as Hispanic dialect, was born due to the Castilian expansion in the XIII century, in contact with Arab language.

Reference courtesy of echaravolar@hotmail.com