A *discriminant* is an expression derived from an equation which gives us some information about the solutions of the equation.

For instance, the discriminant of the quadratic equation \(ax^2 + bx + c = 0\) is \(d = b^2 - 4ac\). In this case:

- if \(d > 0\), the equation has two real solutions;
- if \(d = 0\), the equation has one real solution;
- if \(d < 0\), the equation has no real solutions.