Software Internationalization and Localization

Internationalization and localization are different jobs. Internationalization, often written i18n, is the product design and engineering work that removes barriers to future adaptation. Localization, or l10n, adapts that product for one target locale.

Translation is part of localization, but it is not the whole job. A localized product may need different date, time, number, currency, address, name, keyboard, sorting, and text-direction behavior. W3C describes internationalization as the work that makes those adaptations possible without rebuilding the product.

The useful mental model is this:

stable product data and behavior
  + locale preference
  + locale data and translated messages
  -> locale-appropriate presentation and interaction

Keep the stable facts separate from their presentation. Store an instant as an instant, an amount as an amount, and a person’s name in a form that preserves the information your product needs. Format those values for the locale at the boundary where people read or enter them. Unicode Technical Standard 35 recommends storing and communicating language-neutral data, then formatting it for the client.