Internationalization and localization is what we call the efforts to make WordPress available for people who speak languages other than English. Sometimes internationalization is abbreviated as i18n and localization is abbreviated as l10n. Those abbreviations come from taking the first letter, the last letter, and the number of letters in between the two. Actually the two terms refer to the beginning and the end of the process: internationalization has to be done on the developers' end, while the localization means the translation and adaptation of the script to another language and culture. If you are interested in learning more about the technology used to make the WordPress internationalization possible you can visit the Localization Technology page.
This page is about how to use the localization tools to make your WordPress installation "to speak" in langauges other than the default English.
There are translation files currently available for the following languages:
* Explain how to set up a localized WordPress
If you would like to use WordPress in another language than Englsih, first check the list above whether a translation file is already available or not. If you found the language you are looking for that's great. (If you didn't you might consider reading the article about Translating WordPress, and contributing to the localization efforts.)
define ('WPLANG', '');
Edit this line according to the .mo file you've just downloaded, e.g. for the Portuguese spoken in Brazil you must add:
define ('WPLANG', 'pt_BR');then save it.
Note. If there was an error in the steps above or you did not specified the correct langauge WordPress will default back to English.
If you are fluent in English and another language, creating a translation of WordPress is a fantastic way to contribute to the project and spread the goodness of WordPress. You can read more about this on the Translating WordPress page.
WordPress has some localized sites that will support you in your mother tongue (if available)
If you're interested in how WordPress made localization possible, or if you are a developer who wants to write code for WordPress in a localization-friendly manner, please see Localizing WordPress.