structural:summarization
Voseo

Virtually all dialects of Spanish make the distinction between a formal and a familiar register in the second-person singular and thus have two different pronouns meaning "you": usted in the formal and either tú or vos in the familiar (and each of these three pronouns has its associated verb forms), with the choice of tú or vos varying from one dialect to another. The use of vos and its verb forms is called voseo. In a few dialects, all three pronouns are used, with usted, tú, and vos denoting respectively formality, familiarity, and intimacy.

In voseo, vos is the subject form (vos decís, "you say") and the form for the object of a preposition (voy con vos, "I am going with you"), while the direct and indirect object forms, and the possessives, are the same as those associated with tú: Vos sabés que tus amigos te respetan ("You know your friends respect you").

The verb forms of the general voseo are the same as those used with tú except in the present tense (indicative and imperative) verbs. The forms for vos generally can be derived from those of vosotros (the traditional second-person familiar plural) by deleting the glide, or /d/, where it appears in the ending: vosotros pensá i s > vos pensás; vosotros volvé i s > vos volvés, pensa d ! (vosotros) > pensá! (vos), volve d ! (vosotros) > volvé! (vos).

In Central American voseo, the tú and vos forms differ in the present subjunctive as well:

In Chilean voseo, almost all vos forms are distinct from the corresponding standard tú -forms.

The use of the pronoun vos with the verb forms of tú (vos piensas) is called "pronominal voseo ". Conversely, the use of the verb forms of vos with the pronoun tú (tú pensás or tú pensái) is called "verbal voseo ". In Chile, for example, verbal voseo is much more common than the actual use of the pronoun vos, which is usually reserved for highly informal situations.