Definition:Cartesian Coordinate System/Y Coordinate

Definition
Consider a cartesian coordinate plane with an $x$-axis and a $y$-axis.

Let a point $Q$ be positioned on the plane.

The distance of the line segment from $Q$ to the $x$-axis is known as the $y$ coordinate and (usually) denoted $y$.

If $Q$ is above the $y$-axis, then $y$ is positive.

If $Q$ is below the $x$-axis, then $y$ is negative.

The $y$ coordinate of all points on the $x$-axis is zero.

Also known as
An archaic term for the $y$ coordinate which is sometimes seen is ordinate.

Also see

 * Definition:X Coordinate