No, a pentagon has 5 sides. A four sided shape is called a quadrilateral. An example of a four sided shape is a square or a rectangle. However, there are also other four sided shaped like trapeziums and kites...
An eight sided shape is called an octagon.
A four sided figure is called a quadrilateral.
A tall four sides structure with a pyramid on the top was called
A 12-sided flat-shaped fragment is a dodecagon.
Decogon * * * * * A decagon, actually.
The Washington Monument is shaped as a tall, four-sided pillar with a pyramid at the top. Its shape is called that of an obelisk.
The name of a four sided figure (or shape) is called a Square. :)
A square is a four sided shape but generically they are called Quadrilaterals.