# Different types of polygons

## Notes

Polygons have different names depending on the number of sides and angles.

## Classify polygons

### Many sides, different names

Polygons have different names depending on the number of sides and angles.

• Triangle: three sides and three angles;
• Quadrilateral: four sides and four angles (if all the four sides are the same, it's a square);
• Pentagon: five sides and five angles;
• Hexagon: six sides and six angles;
• Heptagon: seven sides and seven angles;
• Octagon: eight sides and eight angles.

A polygon is called regular if all the sides have the same length and all the interior angles have the same measurement. You'll learn their characteristics soon!

Let's learn the names of some special quadrilaterals:

• Parallelogram: it has opposite sides parallel and equal in length;
• Rectangle: it is a parallelogram where every angle is a right angle (90°). Opposite sides are parallel and of equal length;
• Rhombus: it is a parallelogram where all sides have equal length;
• Trapezoid: it is a quadrilateral that has a pair of parallel opposite sides.

## What is a polygon?

A polygon is a shape bounded by a closed broken line.

A polygon has different elements:

• Sides: all the line segments that compose the broken line;
• Apex: point where two sides of the polygon intersect;
• Surface: part of a plane that is encompassed by the broken line;
• Interior angles: part of a plane between two adjacent segments that meet in an apex.

A polygon has the same number of sides, angles and apexes: if a polygon has 4 sides, it has 4 apexes and 4 internal angles too.