A chord-
A chord is a line segment joining two points on any curve, for instance an ellipse. A chord that passes through a circle's center point is the circle's diameter..

A segment-
segment is the section of a circle enclosed by a chord and an arc. Therefore, those halves of the pizza are segments. If you eat one half, you would have eaten a semicircle (half of a circle), which is the biggest segment of a circle.
Chord is a line segment which join two points in a circle is called chord.segment any of the part which are divided naturallyseparates is called segment.