An ogee is a curved shape consisting of a concave arc flowing into a convex arc and vertical ends. The ogee has a deeply rooted history, being seen in ancient Persia, Greek and Roman architecture, and is heavily used in the Gothic style of the 14th and 15th centuries. The ogee is often seen in windows and arches, as well as the profile of crown and decorative molding.

(Images via southwellchurches, buffaloah, this old house)