Draw a vertical line. Mark numbers: 0 in the middle, positives going up, negatives going down. That is the y-axis, the vertical half of the coordinate system. Together with the x-axis, it pinpoints any location.
What Is the Y-Axis?
The y-axis is the vertical reference line on a coordinate grid. It runs up and down. In the ordered pair (3, 4), 4 is the y-value: after moving 3 right, move 4 up. The y-coordinate is always second.
The y-axis divides the plane into left and right halves. Points to the right have positive x-values; to the left, negative. But the y-axis itself measures vertical distance from origin.
How Do X and Y Work Together?
Think of a city grid. The x-axis is the street (east-west). The y-axis is the avenue (north-south). To find an address, you need both: go 3 blocks east, 4 blocks north. That is (3, 4).
Order matters. (3, 4) is not (4, 3). The first number is always horizontal (x), second is vertical (y). Mixing them puts you in the wrong place. Remember: x comes before y alphabetically, and horizontal comes before vertical when plotting.
Try It: Plot on Y-Axis
Step 1: Draw grid, highlight y-axis, label -5 to 5.
Step 2: Plot (0, 3), (0, -2), (0, 0). All on y-axis because x=0.
Step 3: Plot (2, 4), (-3, -1). Move x first, then y.
Step 4: Plot (4, 3) and (3, 4). See how different they are.
Quick Practice
Question: In (2, -5), what is y? Which direction from origin?
Answer: y = -5. Move 5 units down (negative y is down).
Frequently Asked Questions
How do you remember which is which?
X goes across (like the letter X has crossing lines). Y goes up (like a plant growing). Or: “x before y, horizontal before vertical.”
What if y is zero?
The point sits on the x-axis. (5, 0) is 5 right, 0 up: on the horizontal line.
Are there more axes?
In 3D, yes: the z-axis for depth. But in elementary math, we stick to x and y on flat paper.