Reconstruction:Proto-Germanic/twai

Etymology
From with plural suffix *-i. Compare, from demonstrative root.

Numeral

 * 1) two

Inflection
The declension of this term can not be completely reconstructed. While the genitive, dative, and instrumental forms agree in all descendants where attested, the nominative forms found in Gothic and Old Norse do not match those found in the West Germanic languages. Some of these forms may preserve relics of the Indo-European dual inflection.

Both the Gothic and Old Norse nominative and accusative forms were re-formed by adding adjective endings to a base stem.

In Gothic:
 * Nominative: tw-ai, tw-ōs, tw-a (based on gōd-ai, gōd-ōs, gōd-a)
 * Accusative: tw-ans, tw-ōs, tw-a (based on gōd-ans, gōd-ōs, gōd-a)

In early Old Norse (before the loss of final -u from the neuter plural):
 * Nominative: *twa-(a)iʀ, *twa(i)-aʀ, *tw(a)-u (based on *gōð-(a)iʀ, *gōð-aʀ, *gōð-u)
 * Accusative: *twa-a, *twa(i)-aʀ, *tw(a)-u (based on *gōð-a, *gōð-aʀ, *gōð-u)

In West Germanic, the masculine form was extended with a suffix containing -n- of an unknown origin, to which all languages except Old English have added the regular masculine plural ending of adjectives. The feminine form may have been *twā, possibly contracted from a variant *twa-ō(z) to which the regular feminine plural ending was added. The Old Saxon and Old High German form twō/zwō must go back to an original *twō(z), however.

The neuter form seems to go back to *twai in all West Germanic languages, except for the alternative Old English form which may have been reanalysed in a similar way to Old Norse. However, as the Gothic script does not indicate vowel length for a, the neuter form may have also been twā, in which case it may descend from an earlier *twa-ō, which may descend from an even earlier *twajō in which -j- was regularly lost in late Proto-Germanic. This -ō may have been added to the original *twai to create a new form with inflection parallel to the adjectives, which was retained in the ancestor of North and East Germanic while it was lost again in West Germanic.