0a) Segment: A part of line with two end points is called a line-segment. A line segment is denoted by AB and its length is is denoted by AB.
(b) Ray: A part of a line with one end-point is called a ray. We can denote a line-segment AB, a ray AB and length AB and line AB by the same symbol AB.
(c) Collinear points: If three or more points lie on the same line, then they are called collinear points, otherwise they are called non-collinear points.
(d) Angle: An angle is formed by two rays originating from the same end point. The rays making an angle are called the arms of the angle and the end-points are called the vertex of the angle.
