What is Voseo?
There are several different ways to address other people, ways of saying "you"

Spanish, like many other languages, has several different ways that you can address other people, 
all of which can be translated by the English word "you." 
Spanish has singular and plural forms and also formal and informal ( this also called "familiar")
ways of saying "you," the usage depending on the person you're talking to and/or the circumstances. 
Is the familiar form used to address friends, family, small children and animals
Vosotros (as) The familiar plural form of tú. ( used in Spain) 
Usted ( Ud.) The formal form singular
Ustedes ( Uds.) In Latín América has replaced "vosotros (as)" and is used for both, formal and informal address
when speaking to two or more people
This chart is showing  various ways of saying "you" as the subject of a sentence: 
(singular informal)  usted (singular formal) 
vosotros (plural informal)  ustedes (plural formal) 
The singular informal "tú"  is used when speaking with family members, children, pets, friends or close acquaintances, 
while "usted"  is used when speaking with others. 
the use of  "tú"  suggests a certain amount of intimacy. But the degree of intimacy varies with region.
If you're uncertain which to use, it is usually better to use "usted"  unless until the person starts speaking to you using "tú", 
in which case it is usually OK to reciprocate (unless you're a child or the person speaking to is an authority figure). 
When studying Spanish we must not forget that there are many dialects around. 
A dialect is defined as a language variation which is spoken in a specific territory.
There are important variations in dialect among the various regions of Spain and Latin America.
The differences between dialects are usually limited to intonation, pronunciation and isolated words and expressions.
What we need to remember is that everyone speaks  a dialect, and therefore dialects are NOT incorrect or less valid versions of a language.
One of the main differences between the dialects of Spain and those of Latin America is the use of pronouns.
 In Spain, the informal pronoun that has remained for the second person singular is "tú".
However, some Latin American countries, (Argentina, Uruguay, for example) use "vos", and this is called "voseo".
The pronoun "vos": "vos" is not taught in schools.
In some parts of Latin America, ( Argentina -  Buenos Aires), ( Uruguay) the pronoun "vos" replaces or partly replaces "tú". 
especially in spoken Spanish. 
In some areas, "vos"  implies even greater intimacy than "tú"  does.

"Vos" is used extensively as the primary form of the second-person singular.
The second person plural pronoun, which is "vosotros" in Spain, is replaced with "ustedes" in Rioplatense Spanish (Argentina and Uruguay).
While "usted" is the formal second person singular pronoun, its plural "ustedes" has a neutral connotation and can be used to address
Person/Number       Peninsular (Spain)    Rioplatense (Argentina and Uruguay)
1st sing.                  yo amo                    yo amo
2nd sing.                  tú amas                    vos amás
3rd sing.                  él ama                      él ama
1st plural                  nosotros amamos     nosotros amamos
2nd plural                vosotros amáis          ustedes aman
3rd plural  ellos aman  ellos aman
                                         • Conjugation Charts                                   

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