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About Interface Internationalization
Blender is translated in many languages, and you can select the one you prefer in the User Preferences window, Language & Font section (first enable the International Fonts button, then the chosen language in the middle drop-down list, and finally enable the UI elements you want translated, using the three Tooltips, Buttons and Toolbox buttons).
If you do not activate any button, everything will remain in the default language (i.e. English), so it might be a good idea to only enable the Tooltips one, to have these small chunks of help in your native language, while keeping the interface in its default, English version, which this manual uses for screenshots, reference, etc. (and all its translations should do the same!).