There is no "Define" command in the Proofing group under the Review tab in Word 2016 (see screen shot above), and I cannot find the command listed under "All Commands" in the Customize Ribbon window. This means I am unable to "Install a Dictionary" as explained in the procedure given under the Microsoft Support webpage, found at https://support.office.com/en-us/article/Install-a-dictionary-77BE8DD8-23A0-4E8B-A321-A6F40C9610A5
So how do I get this missing command? How can this be corrected?