There are three areas in Microsoft Office where you might want to change the language.

• Editing is the language in which you write and edit content. You may need to install an associated keyboard for this language through Windows Settings.

• Proofing tools check spelling and grammar. Typically, you set this language to the same as the editing language.

• Display language is for all buttons, menus, and controls in Office.

You can set the display or editing languages independently. For example, you might want the display language to be English, but the document you're writing or editing is in French.

The easiest way to get to the language settings is:
From the Windows Start menu , select Microsoft Office Tools > Office Language settings  (Start  > Microsoft Office verktyg >  Office - språkinställningar). 

On the following page, Micosoft describes how to change the language for these different areas: Change the language used in Office menus and proofing tools (microsoft.com)