The Language property indicates the default language of the content and determines the language dictionary that is used to check the spelling of the document. If you assign a language to a document for which no Developer dictionary exists, the spelling checker skips checking the document.
New documents created from the Library inherit the default language setting. New module, section, and topic documents created in the Outline Editor automatically inherit the language of their parent.
You can also view the Language property for documents in the Details View in the Library or Outline Editor.
Note: The Language property for a topic also determines the publishing styles that are available for preview and the master role list that is used for assigning roles.