• StyleDefinitions is an option for notebooks which gives definitions for the styles that can be used in a notebook.
• StyleDefinitions->"name.nb" specifies that style definitions from the notebook name.nb should be used.
• The standard notebook front end comes with a selection of style definition notebooks containing styles appropriate for particular purposes.
• StyleDefinitions->Notebook[ ... ] allows style definitions to be given explicitly.
• The definition for a style named "s" is specified by the options for the first cell whose contents is StyleData["s"].
• New in Version 3.