ngettext

ngettext is a function used in software localization to select the correct plural form of a translated string based on a numeric quantity. It is part of the GNU gettext framework and is available in C, C++, Python, and many other languages through bindings. The function takes three arguments: a singular form, a plural form, and a number n. It looks up the translation of the singular form in the active translation catalog for the current locale, applies the locale’s pluralization rules to n, and returns the corresponding translated string. If a translation is unavailable, ngettext falls back to the appropriate form of the original English text.

The selection of the plural form depends on the locale’s plural-forms rules, defined in the locale data. The runtime computes a plural index from n and selects the corresponding form from the translated message. Some locales have only two forms, while others, such as Russian or Polish, may have three or more forms. This mechanism allows accurate grammatical agreement for quantities across many languages.

Usage typically involves combining ngettext with the program’s formatting. For example, a line might format the returned string with the number n to produce a message like “There is 1 apple” or “There are 3 apples,” depending on the value of n. In practice, translations are stored in .po files and compiled to .mo catalogs, which are loaded by the application at runtime. Many languages also provide higher-level wrappers or aliases for ease of use.