Definition
Y-intercept
A y-intercept marks a graph’s contact with the vertical axis; its x-value is 0.
What it means
Look for where the graph touches or crosses the vertical axis. Because every point on that axis has x = 0, substituting x = 0 can help locate a y-intercept from an equation.
Remember it
On the y-axis, x is 0.
Example
For y = −3x + 5, substitute x = 0: y = −3 × 0 + 5 = 5. The y-intercept is the point (0, 5), or the value 5 when only the y-value is requested.
Watch for
A graph may fail to meet the y-axis, so not every graph has a y-intercept.
Common mix-up
At a y-intercept, x equals 0. Setting y to 0 finds an x-intercept instead.
Exact meaning
A y-intercept is a point where a graph meets the y-axis. Every y-intercept has x-coordinate 0. In some contexts, “the y-intercept” means the y-value of that point rather than the full ordered pair.