Axiom:Symmetry of Betweenness

Axiom
Let $\mathsf{B}$ be the relation of betweenness.

Then the following axiom holds:
 * $\forall a, b, c: \mathsf{B}abc \implies \mathsf{B}cba$

where $a, b, c$ are points.

Intuition
If a point is on a line segment, it is still on the line segment if you traverse it from the other direction.