Simplify the following text for a Grade 8 native English-speaking person.
Original: In algebra , the discriminant of a polynomial that is equal to zero with real or complex coefficients is a certain expression in these coefficients of the polynomial if and only if the polynomial has a multiple root ( for example , a root with multiplicity greater than one ) in the complex numbers .
Simplified: A polynomial has a multiple root ( i.e. a root with multiplicity greater than one ) in the complex numbers if and only if its discriminant is zero .