Unicode Common Locale Data Repository (CLDR)

The fundamental key for accessing locale-specific data. A Unicode locale identifier uses a standardized syntax (e.g., en_US, fr_CA, zh_Hant_HK) composed of language, script, and region subtags. This system allows for precise targeting, distinguishing between language variants like European Portuguese (pt_PT) and Brazilian Portuguese (pt_BR).

Provides the abstract syntax for formatting temporal data. CLDR defines patterns using LDML (Locale Data Markup Language) date format patterns, such as yyyy-MM-dd or EEEE, MMMM d, y. It handles complexities like the choice between Gregorian, Buddhist, or Hijri calendars, and specifies the correct names for days of the week and months in context.

Defines the rules for numeric presentation beyond simple translation. This includes the correct decimal separator (. vs ,), grouping separators, and percent sign placement. Crucially, it specifies currency codes and their formatting conventions, ensuring that JPY 1,000 is displayed correctly for a Japanese locale.

Encodes the complex grammatical logic for pluralization. CLDR defines CLDR Plural Rules (ordinal and cardinal) for each language, moving beyond simple singular/plural logic. It handles categories like zero, one, two, few, and many, which are essential for generating grammatically correct strings in languages like Arabic or Russian.

Specifies the culturally correct algorithm for sorting text. The Unicode Collation Algorithm (UCA) is parameterized by CLDR data to handle language-specific sorting rules. For example, it ensures that in a Swedish phonebook, the letter 'V' and 'W' are sorted as distinct letters, while in German, 'ß' is sorted as 'ss'.

Provides the localized display names for standardized units. CLDR maps raw measurement codes to their correctly translated and formatted labels. This ensures that a weather app displays temperature in Celsius for a German locale and Fahrenheit for a US locale, and correctly formats units of length, speed, and volume.