Polynomial 

A polynomial in x is of the form:
$p(x)=ax^n+bx^{n1}+cx^{n2}+...+px+q$
Solving $p(x)=0$ will give n roots, some (or all) of which might be complex (see complex number), although some may be repeated roots. For example, $x^22x+1=0$ has two roots, but both are equal to 1.
See also Roots of Polynomials