A **polygon** is a closed plane figure with three or more sides that are
all straight.
Some examples of polygons are shown below.
The following figure is **not a polygon** as it is not a closed figure.
A **circle** is not a polygon as it does not have straight sides.
Polygons are named according to the number of sides. The names of the
most common polygons are given below:
Concave Polygon
If a polygon has a reflex
angle, then it is said to be a **concave
polygon**.
An example of concave polygon is shown below.
Convex Polygon
If a polygon has no reflex
angle, then it is said to be a **convex
polygon**.
Examples of the convex polygons are shown below.
Regular Polygon
A **regular** **polygon**'s sides are all of the same length and
its angles are the same size.
For example, a square is a regular polygon.
Examples of regular polygons are shown below.
Irregular Polygon
If a polygon is not a regular polygon, then it is said to be an **irregular** **polygon**.
For example, the quadrilateral shown below is an irregular polygon.
Key Terms
polygon, triangle, quadrilateral, pentagon, hexagon, heptagon, octagon, nonagon, decagon, undecagon, dodecagon, concave
polygon, convex polygon, regular
polygon, irregular polygon |