What is the Diameter of a Circle: The diameter of a circle is the distance across the circle through its center. It is the longest distance of any point on the circumference of the circle to any other point on the circumference. It is also twice the length of the radius of the circle.
For example, if the radius of a circle is 5 units, the diameter would be 10 units (since 5 x 2 = 10). The diameter is the line segment that connects two points on the circumference of the circle and passes through the center of the circle. It can be represented by the symbol d, where d = 2r (r is the radius).
