Universal 511: Tr ⇒ Du; ¬Du ⇒ ¬Tr;
Du ⇒ Pl; ¬Pl => ¬Du

Universal 511: Tr ⇒ Du; ¬Du ⇒ ¬Tr;
Du ⇒ Pl; ¬Pl => ¬Du

Original

No language has a trial number unless it has a dual. No language has a dual unless it has a plural.

Standardized

IF there is a trial, THEN there is also a dual.
IF there is a dual, THEN there is also a plural.

OR, BY CONTRAPOSITION:
IF there is no dual, THEN there is no trial.
IF there is no plural, THEN there is no dual.

Keywords

number, trial, dual, plural

Domain

inflection

Type

implication

Status

achronic

Quality

absolute

Basis

30 languages of Greenberg 1963 sample

Source

Greenberg 1963: 94, #34

Counterexamples

Northeastern Maidu (Maiduan) (Dixon 1911: 709) is not a counterexample in the strictest sense since indeed there are markers for both plural and dual (in nouns). Yet the dual marker is used more frequently than the plural one, albeit on a very low level: the use of either is rare anyway (Plank 1989: 318).