To change the default language in Microsoft Office Word software, you can try to go to Review tab -> in the Language group, click Set Proofing Language. Finally, in the language box select what option suits you best, and start typing.
To learn how to change the default language used in this application, you can try visiting the following web page and follow the instruction provided there.
To use the Right-to-left language features available in Microsoft Office Word application, you can try visiting the following web page.
