You can always set up multiple custom dictionaries and make sure that each of them is configured to the different languages in which you are working. In other words, if you set the language in step 6 to French, then you won't be able to add any words that are in English, German, Spanish, or some other language.
If you have the custom dictionary set to something other than All Languages in step 5, then Word only lets you add words that are in the language you specified. Close all the open dialog boxes when you are done.At the bottom of the dialog box is the Language drop-down list.In the list of dictionaries, select the one you want to check.Word displays the Custom Dictionaries dialog box. Click on the Custom Dictionaries button.Click Proofing at the left side of the dialog box.
In Word 2010 display the File tab of the ribbon and then click Options.) (In Word 2007 click the Office button and then click Word Options. You can check the language of your dictionary in this manner: Word keeps track of the language of both your text and allows you to specify with what language a dictionary should be associated. The most likely cause for this situation is that the language of the word you are trying to add doesn't match the language of the dictionary. However, when he right-clicks on the word in order to add it to the dictionary, he finds the "add to dictionary" option grayed out, so that he cannot add it. Richard notes that when doing a spelling check in the background, Word dutifully underlines words it thinks are spelled incorrectly.