Voseo is the use of the second person singular pronoun vos and/or its conjugational verb forms in many dialects of Spanish. In dialects that have it, it is used either instead of tú, or alongside it.
Vos is used extensively as the primary form of the second person singular in Rioplatense Spanish for Argentina and Uruguay, and in Paraguayan Spanish, for Paraguay.
El Salvador, Guatemala, Honduras, Nicaragua and Costa Rica also exhibit an extensive use of the vos pronoun through the Central American Spanish dialect. The pronoun is also widely used in Bolivia, though the media use tú more.
Vos had traditionally not been used in formal writing except in Argentina, Paraguay and Uruguay. This gradually changed in Central America, where even the most prestigious media networks and press began to use the pronoun vos, reflecting the informal address in Spanish as opposed to the formal address of usted. This is particularly true in Costa Rica and Nicaragua, and to a similar but lesser extent in El Salvador, Honduras, Guatemala; all of which speak in the Central American Spanish dialect. Nowadays it is very common to see billboards and other advertising media using voseo. In the dialect of Argentina, Paraguay and Uruguay (known as Rioplatense Spanish), vos is also the standard form for use in television media.
Vos is present in other countries as a regionalism, for instance in the Maracucho Spanish of Zulia State, Venezuela (see Venezuelan Spanish), in the Azuero peninsula of Panama, in various departments in Colombia, and in parts of Ecuador (Sierra down to Esmeraldas). In Peru, voseo is present in some Andean regions and Cajamarca, but the younger generations have ceased to use it. It is also present in the Ladino dialect of Spanish, spoken by Sephardic Jews throughout Israel, Turkey, the Balkans, Morocco, Latin America and the United States.
Voseo can also be found in the context of using verb conjugation of vos with tú as the subject pronoun (verbal voseo), as in the case of Chilean Spanish.