plus

   'plus' ['n'|'e'|'f'|'p'|'l'|'s'|'b'|'S'|'L'|'sh'|'si']& ->
          ['a'|'b'|'d'|'n'|'p'|'q'|'t'|'v'] ->
          <set> ['b'|'g'|'k'|'m'|'n'|'r'|'t'|'w'|'y'] [<width>->
                |<transparency>]

This keyword is used to display the entities of an additional set after a plot command was used (see also minus). Further details are explained in section plot.