y-Coordinate — Definition, Formula & Examples
The y-coordinate is the second number in an ordered pair , telling you how far up or down a point sits from the x-axis on a coordinate plane.
In a Cartesian coordinate system, the y-coordinate (also called the ordinate) of a point is the signed perpendicular distance from that point to the x-axis, measured along a line parallel to the y-axis.
How It Works
When you see an ordered pair like , the y-coordinate is . A positive y-coordinate means the point is above the x-axis, while a negative y-coordinate means it is below. If the y-coordinate is , the point lies directly on the x-axis. To plot a point, you first move left or right according to the x-coordinate, then move up or down according to the y-coordinate.
Worked Example
Problem: Identify the y-coordinate of the point and describe its position relative to the x-axis.
Step 1: In the ordered pair , the y-coordinate is the second value.
Step 2: Since is positive, the point is located 7 units above the x-axis.
Answer: The y-coordinate is , and the point sits 7 units above the x-axis.
Why It Matters
Reading y-coordinates correctly is essential for graphing equations, interpreting data on scatter plots, and solving geometry problems on the coordinate plane. In science classes, the y-axis often represents the quantity being measured, so identifying y-values accurately is a skill you will use repeatedly.
Common Mistakes
Mistake: Mixing up the order and reading the first number as the y-coordinate.
Correction: In an ordered pair , the y-coordinate is always second. A helpful memory trick: comes before in the alphabet, just as the x-coordinate comes before the y-coordinate.