Hi
Try following methods to solve the issue:
Method 1: Set Document Language
Method 2: Set the language for the default Normal.dotm template
Method 3: Check the Spelling and Grammar preferences
Method 4: Check the Input Sources language settings
Method 5: Move the Normal.dotm template
Method 6: Remove Word preferences
For detaield information please refer to the link below:
http://support.microsoft.com/kb/2481268/en-us
If you need further help, we recommend you go to Office for MAC forum:
http://community.office365.com/en-us/forums/default.aspx
Sincerely
Tylor Wang
TechNet Community Support
