Two methods:
If you haven't customized your menus at all, you can simply go into Tools |
Customize, select Menu Bar on the Toolbars tab (and only Menu Bar) and click
Reset to restore all main menus to default format.
OR, if you have customized your menus, go into Tools | Customize, click
Commands tab, find Tools in the left column and Language or Set Language in
the right column, you can drag that icon back onto the Tools menu (a
separate Menu Bar toolbar should appear that you drag it onto, rather than
all the way up to the top).
By the way, the Tools | Customize dialog is one of the most helpful dialogs
in Word and you might want to play around with it--you can customize
toolbars, menus, and keyboard shortcuts, and any time you find yourself
doing the same thing over and over again, customizing might be able to save
you some time.
DM