A closed plane figure with three line segments is called a triangle. If the closed plane figure has more than three line segments, it is called a polygon. The word “poly” means “many,” and there are different names for such figures.
A closed plane figure with four line segments is called a quadrilateral. This is the most common type of closed plane figure in geometry. A parallelogram, a rectangle, a square, a rhombus and a trapezium are all examples of quadrilaterals.
A closed plane figure with five sides is called a pentagon. A six and seven-sided figure is called a hexagon and a heptagon respectively. Similarly, a decagon has ten sides, and an octagon has eight sides.