nplurals3

nplurals3 is a term used in internationalization and localization to denote the use of three plural forms in a language’s grammar. It indicates a pluralization rule set in which the count n can map to three distinct form indexes, commonly represented as 0, 1, and 2. The exact semantics of these forms can vary by language, but a three-form system often distinguishes categories such as singular, few, and many.

In translation catalogs such as GNU gettext, the number of plural forms is declared in a header line such as nplurals=3; plural=(expression). The expression computes the zero-based index of the plural form to use for a given count. For three-form systems, the rule typically assigns index 0 for certain singular conditions, index 1 for a small or “few” quantity, and index 2 for larger quantities, though the precise mapping depends on the language and the chosen rule.

Implementation notes: In PO files, the three plural forms would be defined with msgstr[0], msgstr[1], and msgstr[2]. Code using gettext selects the appropriate translation via the plural form index returned by the plural expression. Modern localization libraries based on CLDR or ICU support three-form plural rules, though actual languages using exactly three forms are less common than those with two or more than three.

Relation to tooling: Some frameworks and libraries provide pre-defined three-form plural rules for locales that require them, easing integration but requiring careful locale-specific testing to ensure correct form selection.

See also: plural forms, gettext, ICU message format, CLDR.

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