A kink is a point where a curve dramatically changes direction. The corners of a rectangle are kinks. Kinks can also happen at a point where a curve dramatically changes its the amount it curves. For example a rounded rectangle has kinks where the line segments turn into arcs.

The red points mark the locations of kinks in the curves.

Rhinoceros 5 © 2010-2015 Robert McNeel & Associates. 17-Sep-2015