Application( Cont. Example(dense order) In order to describe dense linear orders we could add into linear order the following sentence vxvy(x<y→3z(x<z∧z<y)Application(Cont.) Example (dense order) In order to describe dense linear orders, we could add into linear order the following sentence ∀x∀y(x < y → ∃z(x < z ∧ z < y)) Yi Li (Fudan University) Discrete Mathematics June 20, 2012 5 / 15