
A few notes on the definition of a polygon that hopefully will help you remember:
The following figures are not enclosed and are not polygons: The following figures are enclosed and are polygons: Types of Polygons There are a lot of types of polygons. Some you've probably heard of before like squares, triangles, and rectangles. We'll learn more about these and others. Polygons are named for the numbers of sides they have. Here is a list of polygon names depending on the number of sides, starting with three and ending with ten.
Convex or Concave Polygons A polygon is either convex or concave. It's convex if any line drawn through it intersects only two other lines. If any line drawn through the polygon can hit more than two other lines, then it's concave. Examples:
In a convex polygon, every angle is less than 180 degrees. In a concave there is at least one angle greater than 180 degrees. Simple and Complex Polygons In a simple polygon the lines don't intersect. In a complex polygon the lines intersect. Examples:
Regular Polygons A regular polygon has lines that are all the same length and it also has all the same angles. Examples: Regular: Not regular: More Geometry Subjects Circle Polygons Quadrilaterals Triangles Pythagorean Theorem Perimeter Slope Surface Area Volume of a Box or Cube Volume and Surface Area of a Sphere Volume and Surface Area of a Cylinder Volume and Surface Area of a Cone Angles glossary Figures and Shapes glossary Back to Kids Math Back to Kids Study 

