An oval is a closed curve in a plane which loosely resembles the outline of an egg. The term is not very specific, but in areas it is given a more precise definition. In common English, the term is used in a broader sense, the three-dimensional version of an oval is called an ovoid. The term oval when used to describe curves in geometry is not well-defined, many distinct curves are commonly called ovals or are said to have an oval shape. Generally, to be called an oval, a plane curve should resemble the outline of an egg or an ellipse, the adjectives ovoidal and ovate mean having the characteristic of being an ovoid, and are often used as synonyms for egg-shaped. In the theory of planes, an oval is a set of n +1 points in a projective plane of order n. An ovoid in the projective geometry PG is a set of q2 +1 points such that no three points are collinear. At each point of an all the tangent lines to the ovoid lie in a single plane. The shape of an egg is approximated by long half of a spheroid, joined to a short half of a roughly spherical ellipsoid. These are joined at the equator and sharing a principal axis of rotational symmetry, although the term egg-shaped usually implies a lack of reflection symmetry across the equatorial plane, it may also refer to true prolate ellipsoids. It can also be used to describe the 2-dimensional figure that, if revolved around its major axis, in technical drawing, an oval is a figure constructed from two pairs of arcs, with two different radii. The arcs are joined at a point in which lines tangential to both joining arcs lie on the line, thus making the joint smooth. Any point of an oval belongs to an arc with a constant radius, but in an ellipse, in common speech, oval means a shape rather like an egg or an ellipse, which may be two-dimensional or three-dimensional. It also often refers to a figure that resembles two semicircles joined by a rectangle, like a cricket infield, speed skating rink or an athletics track, however, this is more correctly called a stadium or archaically, an oblong. Sometimes, it can refer to any rectangle with rounded corners. The shape lends its name to many well-known places, ellipse Stadium Vesica piscis – a pointed oval
A chicken egg is a naturally occurring ovoid
This oval, with only one axis of symmetry, resembles a chicken egg.
An oval with two axes of symmetry constructed from four arcs (top), and comparison of blue oval and red ellipse with the same dimensions of short and long axes (bottom).