What is a 4 sided polygon?

A quadrilateral.

Any ##4##-sided polygon is a quadrilateral.

take many forms, but their most basic characteristic is that they are a ##4##-sided polygon.

In case you didn't know or have forgotten, a polygon is any closed figure created by a series of straight line segments.

In the case of any quadrilateral, there are ##4## of these line segments.

Notice that Latin roots:

"quadri-" means ##4## "latus" means sided