How to Change Display language in MS Word

Step 1: Select File > Options.

Step 2: In the Word Options dialog box, select Language.

Step 3: In the Choose Display Language section, choose the Display Language and Help Language you want to use.
Languages installed in Windows 10 are listed.

If a specific language is not listed, select Get more display and help languages from Office.com.
If necessary, install a Language Accessory Pack, then close and re-launch Word. You may need to reboot your computer as well.
After a language pack loads, go to the Word Options menu and choose that pack in the Display Language and Help Language lists.

Step 4: Select Set as Default for both the Display Language and the Help Language lists.

Step 5: Select OK to save your changes.

Credit : https://www.lifewire.com/change-language-in-word-4173101