def definitiondir(self, filetype, **kwargs):
        """Returns definition subdirectory in :envvar:`PLATELIST_DIR` of the form: ``NNNNXX``.

        Parameters
        ----------
        filetype : str
            File type parameter.
        designid : int or str
            Design ID number.  Will be converted to int internally.

        Returns
        -------
        definitiondir : str
            Definition directory in the format ``NNNNXX``.
        """

        designid = int(kwargs['designid'])
        designid100 = designid // 100
        subdir = "{:0>4d}".format(designid100) + "XX"
        return subdir