Horizontal line appears to be a straight line which is drawn from right to left and in the coordinate plane is parallel to the x axis. In a way the straight line which would be having an intercept on the Y axis and not on the x axis is termed as a horizontal line. A base that we may draw for the flat shapes is termed as a horizontal line. Cuemath is a website where you can obtain considerable amount of information about a horizontal line. It is a one stop website addresses all your needs related to Maths subject.

The definition of a horizontal line

A horizontal line is also termed as a sleeping line. Coming to coordinate geometry, a horizontal line is the one that would be parallel to the x axis. In geometry, a horizontal line segment would be available in numerous shapes like 3d shapes, quadrilaterals, etc.

Slope of the horizontal line

The slope of a horizontal line is zero. When you are calculating the slope rise and the sun, it is seen there is no rise in the y coordinates as it would be the same throughout the coordinate line. No change would be taking place in Y coordinates and hence the slope of the horizontal line would be zero. It would be better to understand things if on a coordinate plane we draw a horizontal line. They are split into a series of steps

  • Step 1 indicates a random dot is to be placed at a single point. An example would be( 2,-3)
  • Step 2 means identification of y –coordinate. Now the y coordinate is – 3
  • Step 3 would indicate plotting of a series of points where the – y coordinate would be the same as the point plotted. Examples would be ( -2,-3) and ( 1,-3)
  • Step 4- there may arise a situation where you would be joining all the points and it has to be extended on both sides for developing a horizontal line.

There is no change when it comes to the point of a horizontal line. A horizontal line would be starting at the right or left point. It is seen that the horizontal line would be 0.

The y coordinates on all the horizontal lines turn out to be the same. X would be absent in most cases. What it means is that x coordinate would be the same in any case whereas y coordinate cannot be anything but has to be the point B on all counts.

The horizontal line test

With the help of a horizontal line test it becomes easy to figure out it is a one on one function or not. As per the test a function does not appear to be one on one if there exists a horizontal line that is going to pass through more than one point of a graph. When it is a one on one function, for every x value there is bound to be a unique y value. In our real life horizontal lines would be present on the steps of the staircase, the planks on the railway tracks.


Coming to the difference between horizontal line and vertical line let us understand in details. Horizontal would indicate side by side, and whereas horizontal line is a straight line. On the other hand vertical line would be up to down. Once again the horizontal lines are drawn from right to left or left to right, which would be parallel to the x axis. It is parallel to the y axis. Both the lines would be perpendicular to each other.