A polygon is a closed 2D shape made of straight line segments connected end to end.
Polygons are classified by the number of sides: triangle (3), quadrilateral (4), pentagon (5), hexagon (6), heptagon (7), octagon (8), nonagon (9), decagon (10), etc. A regular polygon has all sides and angles equal. The sum of interior angles = (n-2) × 180°, where n is the number of sides. Polygons are fundamental in geometry, computer graphics, tiling, and structural engineering.
Polygons have been studied since ancient Greece. Euclid classified polygons in his "Elements." The naming convention uses Greek prefixes (penta = 5, hexa = 6, etc.). Regular polygons are central to the study of geometry and were important in ancient Greek mathematics. The construction of regular polygons with compass and straightedge was a major problem for centuries.