what is a diameter

The diameter of a circle is a line segment that passes through the center of the circle and whose endpoints lie on the circumference of the circle. It is also known as the longest chord of the circle. The diameter is twice the length of the radius of the circle. The symbol used to represent the diameter in engineering is ⌀, which is often referred to as phi. The diameter is an important measurement in geometry, as it is used to calculate other properties of the circle, such as the circumference and area.