Shapes are defined as geometric objects that possess outlines or external surfaces. Common shape names include circle, oval, triangle, square, rectangle, cylinder, star, pyramid and heart.

Shapes often have specific names depending on how many sides they have; a hexagon, for example, has six sides, as the Greek prefix for six is "hex." As there is no limit to how many sides a shape may have, there is no realistic way to compile a complete list of shapes. Shapes can be regularly named, however.

Some commonly understood, and uniquely named, two-dimensional shapes are squares, triangles and circles. Shapes with three through twenty sides often have unique names; above that, the names are constructed based on Greek or Latin prefixes. A 78-sided polygon, for example, would be a heptacontakaioctagon. This name is explained thus: "heptaconta" means "70," "kai," means "and" and "octa" means "eight." The name, translated, would be "70 and 8 sided shape."

These are all polygons, the blanket term for such shapes. Generally polygons can be regular or irregular; regular polygons have the same length of sides and are symmetrical, while irregular polygons are neither. The absolute limit on a polygon's sides is with an apeirogon. This geometric shape is a theoretical, degenerate geometric figure with an infinite number of sides.