# Scientists Say: X-axis

## X marks the spot, and tells you what a graph shows

#### x-axis (noun, “Ex AXE-iss”)

A horizontal line on a graph. It is usually located at the bottom of the graph but can also be at the top or in the middle. Scientists label the x-axis with whatever they are measuring. This might be a list of different items measured. Or it can be a series of numbers that help to show how a variable changes over time.

#### In a sentence

When I graphed how “chewy” people thought cookies were, I put the ingredients in each cookie on the x-axis.

### Power Words

axis   The line about which something rotates. On a wheel, the axis would go straight through the center and stick out on either side. (in mathematics) An axis is a line to the side or bottom of a graph; it is labeled to explain the graph’s meaning and the units of measurement.

x-axis   (in mathematics) The horizontal line at the bottom of a graph, which can be labeled to give information about what the graph represents.

y-axis   (in mathematics) The vertical line to the left or right of a graph, which can be labeled to give information about what the graph represents.

Bethany Brookshire was a longtime staff writer at Science News Explores. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.