Plane Geometry – Why is a Line Segment Not Considered a Polygon?

Question

I understand that polygons are defined by generally all mathematicians as:

Made of three or more straight line segments.

But, two line segments forming a line are also a "poly" of a "gons" due to not having just one segment.

So, I intuitively I as a non mathematician understand simple line segments with "more than one" gon/segment as a "polygon".

Why isn't a line segment considered a "polygon" by mathematicians?

Answer 1

See the definition of the polygon, you will find your answer.

Definition: A polygon is a closed figure where the sides are all line segments. Each side must intersect exactly two others sides but only at their endpoints. The sides must be noncollinear and have a common endpoint.

Note: A circle is not a polygon as it does not have straight sides.