Design Nomenclature / Form & Geometry
Inflection
Also called inflection point, point of contraflexure, reversal
This entry has not been translated yet and is shown in English.
The point where a curve's curvature passes through zero and changes sign — where the bend reverses from one side of the curve to the other. An unintended inflection is a defect: the comb crosses the curve there, a highlight hesitates, an arc quietly becomes an S. Deliberate ones make ogees, entasis, and the spine of a lowercase s.
In practice
'There's a flat in the curve' usually means an inflection nobody meant to draw — three control points gone nearly collinear. Look at the comb rather than the curve; at 1:1 it is invisible and it still shows in the highlight.