Dual (abbreviated DU) is a grammatical number that some languages use in addition to singular and plural. When a noun or pronoun appears in dual form, it is interpreted as referring to precisely two of the entities (objects or persons) identified by the noun or pronoun. Verbs can also have dual agreement forms in these languages.
The dual number existed in Proto-Indo-European. It persisted in many of the ancient Indo-European languages that descended from it such as Ancient Greek, and Sanskrit, which still uses dual forms across nouns, verbs, and adjectives, and Gothic, which used dual forms in...