Answer:
In any given circle, the measure of the radius is 1/2 the measure of the diameter.
Reasoning:
This is because the distance from the center point to any point laying on the circle is equa-distant, meaning equal distances. Therefore, the distance from the center point to any point on the circumference is defined as the radius (or how open the circle is from the center). The diameter is the distance across a circle (or how wide a circle is), so the distance is r+r or 2r because the distance of the radius on opposite sides of the circle are the same, as for any point from the center.