Universal 713: grammatical opposition (Du) ⇒ grammatical opposition (Pl)
Original
If there is any grammatical opposition in the forms of Dual, then there is the same opposition in the forms of Plural.
Standardized
IF any further grammatical oppositions are expressed in forms marked for dual number, THEN the same oppositions will also be expressed in forms marked for plural number.
Keywords
number, dual, plural, inclusive, exclusive, gender, case
1. Inclusive/exclusive opposition in Dual but not in Plural:Coos (Coosan), Lhota (Baric, Sino-Tibetan) (Sokolovskaja 1980: 98);Nomad (Trans-New Guinea) (Voorhoeve 1975: 392, Franklin 1973); Tübatulabal (Uto-Aztecan) (Voegelin 1935: 135, but see also the caveat in Counterexamples to #578); Wik-Munkan (Pama-Nyungan) (Godfrey 1964: 76). Possibly Guató (Macro-Ge) (Pimentel Palácio 1986) 2. Gender distinction in Dual but not in Plural:In Rotokas (W. Bougainville, East Papuan) (Firchow, Firchow, & Akoitai 1973) 2nd person possessive pronouns, and both 2nd and 3rd person subject markers in verbs distinguish masculine and feminine forms in the dual but not in their plural counterparts. Other persons and other kinds of pronoun, however, have the same gender contrasts in both numbers.
1. Cf. #276.2. Cf. a more specific statement by Sokolovskaja, #1490.3. Case distinctions in Dual but not in Plural do not seem to be attested.