How many sides does a triangle have?

A triangle is defined as a polygon that has three sides. This classification comes from the prefix "tri-" which means three, indicating that a triangle includes three edges and three vertices. The sum of the interior angles in any triangle also consistently equals 180 degrees, further solidifying its identity as a three-sided shape. Understanding the properties of triangles is fundamental in geometry, as they serve as the building blocks for more complex shapes and forms. Thus, the correct choice confirms that a triangle indeed has three sides.