The
vos form that
elfbabe describes is actually not only found in
Argentina, but also in the neighboring countries of
Paraguay,
Uruguay, and in
Central America with the exception of
Panama. It also is sometimes used
colloquially in various parts of
Latin America. It is very surprising to me that this
form is usually not taught in
Spanish courses. I have taken Spanish for eight years, and didn't hear about
vos until about a year ago. While I can recognize and comprehend the form, I would not be able to
reproduce it. Note the similarity with the
Portuguese pronoun
você.
The regions that use the vos form, as far as I can divine from my readings, appears to only replace the nominative/subject-form: te remains the object form, tu the posessive.
Some sample conjugations using vos:
quedar to stay
vos te quedás
tener to have
vos tenés
ser to be
vos sos
saber to know
vos sabés
You will notice that stem-changing verbs do not appear to undergo a stem-change in the vos form. Also notice that they are generally accented on the final syllable.