ogee

thumb|right|Two ogee curve examples with their extended S shapes, concave over convex (cyma recta), and convex over concave (cyma reversa), representing the cross section (geometry)|cross-sections of two types of decorative moldings used in building An ogee ( ) is an object, element, or curve—often seen in architecture and building trades—that has a serpentine or extended S shape (sigmoid). Ogees consist of a double curve, the combination of two curves that, as a result of a point of inflection from concave to convex or vice versa, have ends of the overall curve that point in opposite directions (and have tangents that are approximately parallel).

thumb|An ogee arch, showing the pair of component blocks on each side that constitute the double curve of the ogee, joined at its peak by a Keystone (architecture)|capstone. The midpoint of the two blocks on each side that compose the ogee, the point at which the overall curve changes direction, is the [[inflection point referred to in the lead.]] First seen in textiles in the 12th century, the use of ogee elements—in particular, in the design of arches—has been said to characterise various Gothic and Gothic Revival architectural styles. The shape has many such uses in architecture from those periods to the present day, including in the ogee arch in these architectural styles, where two ogees oriented as mirror images compose the sides of the arch, and in decorative molding designs, where single ogees are common profiles (see opening image). The term is also used in marine construction, particularly in shipbuilding, where ogee curves are used in hull design to improve hydrodynamics. The word was sometimes abbreviated as o-g as early as the 18th century, and in millwork trades associated with building construction the term is still sometimes written similarly (e.g., as O.G.).