Voseo (Spanish pronunciation: [boˈse.o]) is the use of vos as a second person singular pronoun, including its conjugational verb forms in many dialects of Spanish. In dialects that have it, it is used either instead of tú, or alongside it. Use of "tú" is known as "tuteo".
Vos is used extensively as the primary form of the second person singular in River Plate Spanish (Argentina, Uruguay, eastern Bolivia), and Paraguayan Spanish.
The Central American Spanish (El Salvador, Guatemala, Honduras, Nicaragua, Costa Rica, southern parts of Chiapas in Mexico) also exhibits an extensive use of vos, though...