A quadratic is an expression or an equation that contains the variable squared, but not raised to any higher power. For instance a quadratic equation in x contains x ² but not x ³. Similarly a quadratic expression, or a quadratic form, contains its variable(s) squared but not raised to any higher power. If there is more than one variable (say, x and y), quadratic can mean that they are multiplied together in pairs (xy) but not in threes (such as x ²y). The graph of a quadratic equation is known as a quadratic curve; the curve of the general quadratic equation y = ax ² + bx + c is a parabola.