When you have finished this page and think you are ready, go to the Lines, Rays, Angles Quiz.

A point is a location in space.

point image

A line is a collection of points along a straight path that goes on and on in opposite directions. A line has no endpoints.

Line animation


A line segment is a part of a line having two endpoints.

Line segment image


A ray is a part of a line with one endpoint and goes on and on in one direction…

ray animation

Parallel lines are lines that never intersect or cross one another.


parallel lines image

Perpendicular lines cross each other or intersect at right angles.

perpendicular lines


An angle is two lines that meet at an endpoint called a vertex. An angle can be named by the three letters that form it or by the letter that is at its vertex. An acute angle is one that measures less than 90 degrees with a protractor – that is how much the angle is open or the lines diverge from the vertex.


This would be A on the angle.
Vertex or Point B of the angle acute angle image This would be C on this angle
Acute Angle ABC or Angle B


An obtuse angle has a measure of greater than 90 degrees at its opening as measured by a protractor.

Obtuse angle image


Straight angle image

Two angles whose measure in degrees adds up to 180 degrees are supplementary angles. An angle of 180 degrees is a straight angle and looks exactly like a line. In the above picture, A and B are supplementary to one another.