A Web site defines a regular polygon as "a polygon with all sides the same length." Is this definition valid?

A. Yes, because all regular polygons fit this definition.

B. Yes, because a square is a regular polygon.

C. No, because some polygons that are irregular fit this definition.

D. No, because not all regular polygons fit this definition.

In geometry, a polygon is called a regular polygon whose sides and interior angles are equal to each other.

The regular polygons of three and four sides are called equilateral triangle and square, respectively. For polygons of more sides, the regular term is added (regular pentagon, regular hexagon, regular octagon, etc).

Answer:

A. Yes, because all regular polygons fit this definition.