The bottom portion of the Dictionary menu contains a list of your dictionaries. Excalibur uses the checked dictionaries in its spell checking operation. You can check and uncheck dictionaries before you begin the spell check operation. Once you have begun, you can't change them. You can change dictionaries between spell checking operations. Any dictionary that is checked is an active dictionary. If a dictionary name appears in plain text, it is modifiable. That is, you can add words to it. If the name appears in italics, the dictionary is read only.