A closed figure made up of line segments is called a polygon. The segments in a polygon are called sides or edges.
If the line segments are straight, then it is a triangle.
Polygon.
a closed figure with all straight line segments is called a polygon.
a closed plane figure with 3 or more line segments is a polygon
A 5 sided pentagon
A triangle.
A polygon, if all the line segments are in the same plane.
That is called a polygon.
A polygon.
A Polygon
It is called its perimeter.