When was the dual number used in Attic Greek?

1. What is dual number in ancient Greek?
2. Which languages have dual number?
3. What is dual number of pronouns in Old English period?

What is dual number in ancient Greek?

In Koine Greek and Modern Greek, the only remnant of the dual is the numeral for "two", δύο, dýo, which has lost its genitive and dative cases (both δυοῖν, dyoīn) and retains its nominative/accusative form. Thus it appears to be undeclined in all cases.

Which languages have dual number?

Today, the dual survives only in two Indo-European languages, Slovenian and Sorbian, both from the Slavic subfamily. In English the loss of the dual was a slow process, taking place over thousands of years.

What is dual number of pronouns in Old English period?

Dual pronouns function the same was as any personal pronoun, but have only two forms: the first person and the second person. A modern translation of the Old English dual pronouns would be 'us two' and 'you two', and like all pronouns they decline differently depending on their case.