This question cannot be answered without more information. For a relationship to exist, you need two items. Only one is Ben - the diameter? What is the other? Area? Circumference? Radius? Please review your question and add the other component, thn it can be answered.
The radius is half the diameter of a circle.
The diameter of any circle is twice its radius
diameter times pi(3.14159) equals cicumference
The radius is half the diameter.
The circumference is pi times the diameter.
The relationship between the radius and the diameter of a circle is that: radius = diameter /2
The radius is half the diameter of a circle.
Circumference of a circle is approximately 3.1416 times the diameter of the circle.
The diameter of any circle is twice its radius
It is 90 degrees between the circle's diameter and its tangent
diameter times pi(3.14159) equals cicumference
The diameter of a circle if twice the length of the radius.
The radius is half the diameter.
The circumference is pi times the diameter.
pi
Circumference = diameter x pi
The diameter is the distance across the circle. So if you split the circle in half by drawing a line through it, the diameter would be the length of that line.