  We extend Reider's freeness criterion to normal surfaces of characteristic 0.
  Let Y be a normal surface.
  Let D be a nef divisor on Y such that K_Y+D is a Cartier divisor.
  Let x be a point on Y.
  If x is a base point of |K_Y+D| and D^2>\delta_x (\delta_x is determined by
x, \delta_x <= 4) then there exists a non zero effective divisor E on Y passing
through x such that
  0 <= DE <= \delta_x /2,
  DE - \delta_x /4 <= E^2 <= (DE)^2 / D^2,
  E^2 < 0 if DE=0.
