What is "vos"??
What is VOS?
Vosotros is the plural form.
¿De dónde SOS?, ¿Cuántos años TENÉS?, ¿Y VOS?.
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These questions quickly confront anyone who comes to Buenos Aires or any other city in the vicinity of Rio del Plata. Even if you are an experienced Spanish speaker you may be surprised when you first hear these pronouns and verb forms. So what in the world is VOS?
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“VOS” is the second-person singular pronoun – it replaces the more common pronoun “TÚ” that is used in most other Spanish-speaking countries. It is the equivalent of the English “YOU” when used to address a single individual. VOS has its own set of verb forms that are distinct from those used with other pronouns.
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For example:
Vos sos una buena persona. (Here “sos” replaces “eres” that is normally used with “TÚ”)
You are a good person.
Note that “VOS” is the informal form of address. For formal means of addressing a single individual use “USTED” the same way it is used in Spain or other Spanish-speaking countries. The use of “VOS” is referred to as “voseo”. In Argentina it replaces “TÚ” completely. You will never hear anyone use “TÚ” in Buenos Aires (but people will understand you perfectly if you use it). VOS and Standard Spanish
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Sometimes students looking for a Spanish course get concerned that Argentinian Spanish is non-standard. “Will I be able to speak Spanish elsewhere if I learn all this VOS stuff?” – they wonder. In practice this is never a problem. First, all you have to know about VOS is described in this article. Secondly, if you learn Spanish in Argentina you will have no difficulty in understanding or using “TÚ”. All Spanish teachers in Argentina make it a point to teach both forms. Conversely, if you already learned Spanish elsewhere Argentinians will understand you perfectly. Conjugations of VOS.
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When using vos, verbs are conjugated differently in just two cases: Indicativo Presente and Imperativo Affirmativo. All other conjugations are the same as “TÚ”. VOS in Indicativo Presente.
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The Indicativo Presente form of VOS is actually easier to remember than that of any other pronoun. It always follows on simple rule:
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1-Replace the last “R” with “S”
2-Add an accent over the last vowel.
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Accordingly the VOS form of a verb is pronounced differently than “TÚ” because stress is always on the last syllable. Here are the conjugations for VOS in Indicativo Presente.
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......................HABLAR COMER VIVIR
TÚ ........... hablas ..... comes ..... vives
VOS .............hablás ......comés ...... vivís
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There is only one exception: Indicativo Presente of the verb SER for VOS is SOS.
Example:
Tú eres medico.
Vos sos medico.
You are a doctor.
VOS in Imperativo Affirmativo.
The formation of Imperativo Affirmativo for VOS is also very easy. The rule is as follows:
Drop the last “R”
Add an accent over the last vowel.
Accordingly the VOS form is pronounced with the stress always in the last syllable. Here are the conjugations of regular verbs in Imperativo Affirmativo:
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............ HABLAR ....COMER .....VIVIR
TÚ .......... habla .... come .......vive
VOS ........ hablá ...... comé ..........viví
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There is only one exception: the Imperativo Affirmativo conjugation of IR is ANDÁ. Here are conjugations in Imperativo Affirmativo for some common irregular verbs.
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......SER ... IR ....SABER
TÚ ........ sé ...... ve ........ sabe
VOS........ sé ... andá ..... sabé
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Note: In Imperativo Negativo VOS is conjugated the same way as “TÚ”.
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The History of VOS
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VOS comes from the second person plural pronoun YOU in Latin (also VOS). Around V century the plural form VOS started to be used to address the Roman Emperor as a sign of respect because the Emperor represents the people. Later his use of plural YOU has spread to other social groups as a general form of polite address. Many languages still retain this influence. For example in French the plural VOUS is used to address a single person in a formal way.
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In Spain and it’s colonies the use of VOS evolved to replace TÚ even in informal contexs such as among friends and family. Thus VOS lost its original purpose as a means of polite address of people in authority.
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The Spanish aristocracy then came up with a new mode of polite address VUESTRA MERCED which later with time became abbreviated into the now common USTED.
With the rise of USTED as a formal way of address TÚ made a comeback in Spain and regained its original use as a familiar form of YOU. The use of VOS correspondingly declined. However, the countries such as Argentina that were less connected to the Spanish Empire and thus were less influenced by its fashions have retained the use of VOS for the familiar form of address that was common when the country was originally settled.
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More info here
35 Answers
En azul oscuro y azul claro los países con predominancia del voseo. En verde, los países donde la práctica se restringe a algunas zonas y en celeste, aquellos países donde su presencia es proporcionalmente pequeña. En rojo, la República Dominicana, España, Guinea Ecuatorial y Puerto Rico, donde el voseo no se usa nunca.
Countries that feature voseo.
Dark blue: countries that use vos as the primary spoken and written form.
Medium blue: countries where voseo is predominant, yet not as intensive.
Green: countries where the use of voseo is regional.
Light blue: countries where the presence of voseo is proportionally small.
Red: countries where voseo is practically non-existent.
Benz
You won't get many answers to this - you have answered everything yourself. 
I just came across this form again from Honduras so I was glad to find this informative post. Maybe I should bump it up again.
How do you use it in un mandato with a pronoun?
ie. Vete
Would it be like... Andásos???
That sounds weird to me.
The imperative mood of the verb "ir" is :
ve (tú) / andá (vos)
id (vosotros) / vayan (ustedes)
Argentinians use "andáte" too:
"¡Andáte nomás!" (Go away!)
The legendary " Benz" has left a comment of this wonderful thread
I thought that it deserved bumping up , and to remind everyone what
a great member that we have in"Benz".She helped so many of us to
come to grips with her beautiful language , I shall never forget her.
Without great members like "Benz" SD would not have lasted so long.
Thank you dear friend , my dearest hope is that you will return
You've touched my heart ray76!! I miss many people from this forum, including you!!!!
Tocaste mi corazón ray76!! Extraño a mucha gente de este foro, incluyéndote a vos! - Benz
I have never had the chance to thank "Benz" for this and all of her excellent
work on SD. She was also the moderator on my very first thread on SD .
Thank you so much old mate , I miss you greatly. You are a Leyenda
I don't want answers Ian 
This is just information for you... learners of Spanish!!! It's good info and if I don't post it here, where should I post it? I think I'll link it to the Reference thread I opened some time ago...
Thanks anyway Ian 
Ask all and everything you want to know about the use of "vos"... I'm here to answer your questions
Do you drop r and and add i for the preterite. For example in song title I saw enojai instead of enojaste.
I'm still contemplating Argentina for next year so this is good to know.
I still remember a week I spent in the southernmost point of Chile with my parents and a guide from Argentina. I and the guide got along well and we both attempted to show a level of informality but failed utterly. He kept using vos and I kept using tú. One of us eventually asked the other why they were being so "formal". We got a good laugh out of it.
I should add that the teenagers in Chile seemed to use an extremely informal manner of address that could be described as voseo but sounded a lot more like the vosotros form. e.g. ¿Cómo estáis? which in true chilean teen fashion was pronounced "¿Cómo 'tai'? The "e" and "s" inevitably got swallowed.
This is great, thanks! Benz do we also use the pronoun TE with voseo? Ponételo? Andáte?
Bumping para todos.
Nice information
Interesante... se usa 'voseo' en México.
