Definition:Discriminant of Polynomial/Quadratic Equation

Definition
Consider the quadratic equation:
 * $a x^2 + b x + c = 0$

The expression $b^2 - 4 a c$ is called the discriminant of the equation.

Also see
Note that this is a special case of the general discriminant, although it is important to note that the general formula is given for monic polynomials.