(i) Line segment: The part of a line that connects two points or we can say that a shortest distance between the two points. A line segment is one-dimensional.
Here AB is a line segment.
(ii) Collinear points: Two or more points are said to be collinear if all the points lie on same line.
(iii) Parallel lines : Two lines in a plane are said to be parallel lines if they do not intersect each other.
Here l and m are parallel lines.
(iv) Intersecting lines: Two lines are intersecting if they have a common point. The common point is known as point of intersection.
Here l and M are intersecting lines. And P is point of intersection.
(v) Concurrent lines: Two or more lines are said to be concurrent if there is a point which lies on all of them.
Here l, m and n are concurrent lines.
(vi) Ray: A straight line extending from a point indefinitely in one direction only.
Here OA is a ray.
(vii) Half-line: If A, B. C be the points on a line l, such that A lies between B and C, and we delete the point A from line l, the two parts of l that remain are each called a half-line.