Piecewise-circular curves

A crescent shape (, ) is a symbol or emblem used to represent the lunar phase (as it appears in the northern hemisphere) in the first quarter (the "sickle moon"), or by extension a symbol representing the Moon itself.

Reuleaux polygon with three sides

right|thumb|Interlaced triquetra which is a trefoil knot The triquetra ( ; from the Latin adjective triquetrus "three-cornered") is a triangular figure composed of three interlaced arcs, or (equivalently) three overlapping vesicae piscis lens shapes. It is used as an ornamental design in architecture, and in medieval manuscript illumination (particularly in the Insular tradition). Its depiction as interlaced is common in Insular ornaments from about the 7th century. In this interpretation, the triquetra represents the topologically simplest possible knot. thumb|Comparison of associated Reuleau

shape that is the intersection of two circles with the same radius

thumb|Quatrefoil above the west door of Croyland Abbey showing in [[relief scenes from the life of Saint Guthlac]] thumb|Quatrefoil window at the St. Petrus parish church in Peterslahr, Germany A quatrefoil (anciently caterfoil) is a decorative element consisting of a symmetrical shape which forms the overall outline of four partially overlapping circles of the same diameter. It is found in art, architecture, heraldry and traditional Christian symbolism. The word 'quatrefoil' means "four leaves", from the Latin , "four", plus , "leaf"; the term refers specifically to a four-leafed clover, but

shape

thumb|right|300px|The salinon (red) and the circle (blue) have the same area.

150px|thumb|right|Architectural trefoil

plane curve drawn by an odd number of circular arcs

2D shape

curve of constant width

In geometry, a cyclogon is the curve traced by a vertex of a regular polygon that rolls without slipping along a straight line.

two-dimensional geometric shape constructed of a rectangle with semicircles at a pair of opposite sides

shortest path with bounded turning radius

triangle with circular arc edges