Non-convex polygons

A non-convex polygon is a simple polygon that is not convex. That is, there exists at least one pair of points inside the polygon such that the segment joining them passes outside the polygon. Equivalently, a polygon is non-convex if at least one of its interior angles is greater than 180°.

Important properties

• At least one interior angle is greater than 180°.

• The line segment between some pairs of points inside the polygon may leave the polygon.

• Non-convex polygons can have 'indentations' or 're-entrant' vertices.

• The sum of the interior angles is still (n-2) × 180°, where n is the number of sides.