Axiom:Parallel Postulate

Axiom

 * If two straight lines are drawn which intersect a third in such a way that the sum of the measures of the two interior angles on one side is less than the sum of the measures of two right angles, then the two lines must intersect each other on that side if extended far enough.

Also see

 * Axiom:Euclid's Fifth Postulate: This is the name and formulation by which Euclid's Fifth Postulate is usually known. As can be seen, its wording in its modern format gives it an intent very similar to 's.