Is a triangle a regular polygon?

A triangle may or may not be a regular polygon. Let's look into things.

First, a triangle is a polygon. All triangles are polygons. To be a regular polygon, the polygon must have equal sides. If the triangle has sides of equal length, then that triangle is an equilateral triangle and a regular polygon. If the triangle doesn't have sides of equal length, then it isn't a regular polygon. But in any case, the triangle is a polygon.