während

Etymology
From the present participle of, with resegmentation of währendes [noun], währender [noun], währendem [noun] as während des [noun], während der [noun], während dem [noun].

Conjunction

 * 1) while

Preposition

 * 1) during, at the time of

Usage notes
1. In the standard language, während is usually followed by the genitive, but bare nouns (not preceded by an article, determiner, or adjective) are usually not declined (they are used in the nominative):
 * Ich wurde während eines Gesprächs angerufen. – "I was called during a conversation."
 * Während Umbau geschlossen.


 * The dative case is used if the genitive is indistinguishable from the nominative, which is the case with plural bare nouns:
 * Ich wurde oft während Gesprächen angerufen. – "I was often called during conversations."


 * The dative case is also used with pronouns that do not have a genitive form, and if a possessive genitive precedes the referent of the preposition.
 * Ich wurde während etwas Wichtigem angerufen. – "I was called during something important."
 * Ich wurde während Peters langem Vortrag angerufen. – "I was called during Peter's long speech." (→ während Peters langen Vortrags is possible, but unusual)

2. In colloquial language, and occasionally in writing, it is common to use the dative case after während at all times, whereby the above peculiarities cease to apply. To some, the genitive may even sound pretentious in a private conversation.
 * Ich wurde während einem Gespräch angerufen. – "I was called during a conversation."