Chord
A chord is a straight line segment whose endpoints lie on the circumference of a circle. The longest chord of a circle passes through its center and is called the diameter.
Example
Consider a circle with center $O$. A line connecting point $A$ on the circle to point $B$ on the circle forms the chord $AB$. If a perpendicular line is drawn from the center $O$ to the chord $AB$, it bisects the chord into two equal segments.