A polygon that is always regular is the equilateral triangle.
Regular polygons are defined as shapes where all sides are of equal length and all angles are of equal measure. While there are many types of polygons, the equilateral triangle stands out because it is the simplest polygon with these properties. Every equilateral triangle has three sides, all of which are equal, and all internal angles measure 60 degrees.
In contrast, other types of polygons, such as quadrilaterals or pentagons, can be irregular or regular depending on their specific side lengths and angles. Thus, the equilateral triangle remains the only polygon that is inherently regular.