Hello,
Open Start > Settings > Apps > Apps & features.
Check if you've Microsoft Office listed there. If it is in the list of installed programs then select the entry and then select Modify. There should be an option to Repair the installation.
Choose the type of repair you would like to perform. Depending on the severity or availability of your Internet connection, you could try the first option, Quick Repair, which is much faster and tries to fix the problem without a data connection.
If that doesn’t resolve the problem, then go back and try the Online Repair option.
The repair process is straight-forward following the wizard. Note that you’ll need to save your work and close all Office programs first, and then click Repair.
Then wait while the repair process runs.
You will notice the repair experience is similar to a fresh installation. The amount of time it takes will depend on your connection speed and what the issue is.
You will see your Office apps light up in their respective colors while the repair completes.
Reboot your system and check if you can launch Microsoft Office apps then.
In case if issue still persists, you need to reinstall Microsoft Office.
So if you have Microsoft/Office 365 subscription or your Office product key, download the setup media directly from https://setup.office.com.
Hope this helps!
Referenced from Andre's post at https://answers.microsoft.com/en-us/windows/forum/all/missing-microsoft-word-after-last-windows-10/b3a7acfc-671a-44a2-9221-59b065512dd4.