word 2011 and 2016 : use both!

https://en.wikipedia.org/wiki/Microsoft_Office_2016
better:
https://fr.wikipedia.org/wiki/Microsoft_Office_2016
https://fr.wikipedia.org/wiki/Microsoft_Office_2016_pour_Mac

Should you remove Office for Mac 2011 after installing Office for Mac 2016?

Users are asking if they should remove Office for Mac 2011 and their Outlook 2011 Identities after installing Office for Mac 2016.

You should not remove Office for Mac 2011 before updating to Office for Mac 2016. After you have successfully installed Office 2016 and imported all your data from Outlook 2011, you can select to remove or leave the old version.

Users with lots of free drive space, do not need to remove Office 2011.
Users on small SSD drives will most likely want to remove Office 2011.
Make sure you keep both versions upgraded. Current versions (Nov 25, 2015)

Office 2011 v 14.5. 8
Office 2016. v 15.16.0

Pros

Word and Excel 2011 have features that were not added to the 2016 versions.
If for some reason Outlook 2016 had issues and could not connect, you might find having Outlook 2011 around to get email would be an added bonus.
If a bad update broke your Office 2016 apps, you can revert to 2011 version until you resolve.

Cons

While you can switch back and forth between Outlook 2011 and 2016, keeping them in sync will depend on the type of accounts you have.  If you have POP accounts you will need to export new emails from 2011 to 2016 as .olm and import into your Outlook 2016 Profile (Identity).

Remove Office for Mac 2011

Follow the directions here to manually remove Office 2011. The “Remove Office” app is no longer available and even old versions of Remove Office did not get everything.

Be sure to remove the Microsoft User Data folder in Documents. This folder is no longer used by Office for Mac 2016. It contains your Outlook Identities.  Outlook 2016 Profile (Identity) is stored in your User’s Library. See Location of Outlook 2016 Profile (Identity) for help locating your Profile (Identity)

The Microsoft fonts folder in the main Library/Fonts folder is no longer used by Office for Mac 2016 and can be removed. Delete font caches after removing fonts. I suggest Font Nuke.

Empty the Trash  to free up the space on your drive.

http://www.officeformachelp.com/2015/11/should-you-remove-office-for-mac-2011-after-installing-office-for-mac-2016/

differences between mac OSX and  MS win

https://9to5mac.com/2016/01/21/windows-mac-ipad-microsoft-office-comparison/