TRUE RADIUS means that the arc is part of a circle. The height must be less than or equal to half the width of the unit.
HALF CIRCLE means that the height is exactly half the width. A true half circle is a true radius, but a true radius but a true radius does not have to be a true half circle. (i.e. Eyebrow)
EYEBROW is a true radius but not a true half circle. (See drawing below)
ELLIPSE is made using two or more radii.
GOTHIC means that the height must be greater than half the width.
SPRING LINE is the point where radius or curved portion meets straight vertical legs.
CENTER LINE is the measurement from the bottom of the unit to the top of the radius.
DROP is the measurement from the top of the unit to the spring line.
