Answer: diameter
Explanation: A diameter is a chord that contains the center of the circle. A chord is just a segment whose endpoints lie on a circle.
A diameter is composed of two radii which is a segment that joins the center of the circle to a point on the circle. All radii are congruent.
In the image provided, I have bolded P and M because they form the diameter of the circle which remember is a chord that contains center of the circle.
