y (variable)
A letter often used for the dependent variable: the output whose value depends on x, as in y = 2x + 1.
y-axis
The vertical number line that passes through the origin on a coordinate plane.
y-axis symmetry
A graph has y-axis symmetry if folding it along the y-axis makes the left and right halves match: whenever (x, y) is on the graph, so is (−x, y). Even functions have this symmetry.
y-coordinate
The second number in an ordered pair (x, y). It tells how far a point is above or below the origin; also called the ordinate.
y-hat
The symbol ŷ, a y with a hat over it, which stands for a predicted value from a regression line or model.
y-intercept
The point where a line or curve crosses the y-axis. There the x-value is always 0, so the point is written (0, b).
Yard
A US customary unit of length equal to 3 feet or 36 inches, a little less than a meter (0.9144 m).
Year
The time it takes Earth to travel once around the Sun: 365 days, or 366 in a leap year. A year has 12 months, or about 52 weeks.
Yield
In finance, the income an investment earns, usually written as a percent of its value per year.