Du (personal pronoun)

Du is a common Germanic second-person personal pronoun that can be found in many of the modern Germanic languages.

Germanic languages

Scandinavian languages

In Swedish, du is nowadays used on both informal and formal occasions due to reform in the 1970s.^{[citation needed]} This means one can address anyone including nobility and politicians with du.^{[citation needed]} However, it is rarely used when addressing a member of the Swedish royal family.^{[citation needed]}

Du is also used in Danish and Norwegian.

In Icelandic, the equivalent pronoun for the nominative second person singular is þú.

English

In English, though obsolete in most dialects, the historical and etymological equivalent pronoun is thou. You, which was originally used for the plural or as a polite singular, is used today for both numbers and regardless of social context.

German

In German, du is only used as an informal pronoun. It is only addressed to persons that one knows very well, like family members and close friends. It is also most commonly used among young people. In formal cases one uses Sie.

Equivalents in other languages

In Romance languages like Spanish, Portuguese, Italian, and French, as well as in Baltic languages (Lithuanian, Latvian) the direct equivalent is tu (or tú in Spanish). Du and tu have a common Indo-European root.
In Slavic languages the equivalent is ty or ti (ты, ти in Cyrillic script) with the same Indo-European root.

References

Du in Danish language: http://da.wiktionary.org/wiki/du and http://www.ordbogen.com/opslag.php?word=you&dict=a000#daen
Du in Norwegian language: http://no.wiktionary.org/wiki/du