Terminology of Curved Window Shapes
True Radius means that the arc is part of a circle. 
Half Circle means that the height is exactly half of the width.
Eyebrow/Segment is a true radius but not a true half circle.
Spring Line is the point where the radius or curved portion meets the straight vertical legs.
Ellipse is a curve with two or more radii and often requires a template.
  Half Round/Circle Top Eyebrow/Segment Full Circle  
  Quarter Circle Gothic Head Quarter Eyebrow/Segmental  
  Oval (Not True Radius) Elliptical Quarter Ellipse  

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