Order Property
We say that the formula φ(x;y) := φ(x1,…,xn;y1,…,ym) has the order property in the model M if there are an infinite sequence a0, a1, … of n-tuples from M and an infinite sequence b0, b1, … of m-tuples from M so that
φ(ai;bj) ⇔ i ≤ j

 
We say that φ(x;y); has the order property (relative to the theory T) if it has the order property in some model of T. A theory T is stable if and only if no formula has the order property relative to T.
 
Starting from an instance of the order property
(M, φ(x;y), {ai | i ∈ &omega}, {bi | j ∈ &omega})
setting
ci := ai bi
and
ψ(u1, …, um+n;v1, …, vm+n) := φ(u1, …, un;vn+1, …, vm+n)
then &psi defines an infinite linear order on the set of tuples {ci | i ∈ &omega }.