Introduction to Geometry and Polygons
Geometry comes from Greek words meaning "earth measurement" and helps us understand shapes and spaces. Solid geometry deals with three-dimensional figures, while mensuration focuses on measuring geometric magnitudes like lengths, areas, and volumes.
A polygon is a closed plane figure with three or more angles (from Greek: "poly" meaning many, "gonin" meaning angle). Polygons are named by their number of sides—triangles have 3 sides, quadrilaterals have 4, pentagons have 5, and so on up to complex shapes like the dodecagon (12 sides) or even the chiliagon (1000 sides)!
Regular polygons have all sides equal and all interior angles equal. Polygons can be either convex (all interior angles less than 180°) or concave (at least one interior angle greater than 180°).
Quick Tip: When identifying polygons, count either the sides or vertices (corners)—the number will always be the same!