A girl sits on a swing.
A girls sit on a swing.
If a girl is sitting on a swing and a girl is on a swing then there is more than one girl on a swing
exists e1 x1 x2.(on(e1,x2) & n_swing(x2) & Actor(e1,x1) & v_sit(e1) & n_girl(x1))
exists e1 x1 x2.(on(e1,x2) & n_swing(x2) & Actor(e1,x1) & v_sit(e1) & n_girl(x1))