14sided

14sided, in geometry, commonly refers to a polygon with fourteen sides, called a tetradecagon (also tetradecagon or tetrakaidecagon). A 14-sided polygon has 14 vertices and 14 edges. The interior angle sum is (n − 2) × 180° = 12 × 180° = 2160°, so a regular tetradecagon has each interior angle equal to 2160°/14 ≈ 154.29°, and each exterior angle 360°/14 ≈ 25.71°. A regular tetradecagon can be drawn with all sides and angles equal in principle, but a regular 14-gon is not constructible with classical straightedge and compass, since 14 = 2 × 7 and 7 is not a Fermat prime.

A tetradecagon need not be regular; irregular 14-sided polygons are common in geometry and computer graphics. The term can also describe regular star polygons with 14 sides, using the Schläfli symbol {14/k} for certain k with gcd(14, k) = 1, e.g., {14/1} (the convex 14-gon), {14/3}, and {14/5} as star polygons.

In another context, 14sided can refer to the 14-faced die used in tabletop games, based on a deltohedron (a tetragonal trapezohedron). Each face is a kite shape, and the die is labeled from 1 to 14.

Nomenclature: tetradecagon is the standard geometric term; tetrakaidecagon is a less common synonym, both meaning a 14-sided polygon.