Right-click the Start button 
(lower-left corner), and select Apps and Features on the pop-up menu.
Select the Microsoft Office product you want to repair, and select Modify.
Note: This will repair the entire Office suite even if it’s just one application you want to repair such as Word or Excel. If you have a standalone app installed, then search for that application by name.
Depending if your copy of Office is Click-to-run or MSI-based install, you’ll see the following options to proceed with the repair. Follow the steps for your installation type.
Click-to-run
In the window How would you like to repair your Office Programs, select Online Repair > Repair to make sure everything gets fixed. (The faster Quick Repair option is also available, but it only detects and then replaces corrupted files.)
MSI-based
In Change your installation, select Repair and then click Continue.
Follow the instructions on the screen to complete the repair.