High Quality Content by WIKIPEDIA articles! In statistical modeling (especially process modeling), polynomial functions and rational functions are sometimes used as an empirical technique for curve fitting. A polynomial function is one that has the form y = a_{n}x^{n} + a_{n-1}x^{n-1} + cdots + a_{2}x^{2} + a_{1}x + a_{0} where n is a non-negative integer that defines the degree of the polynomial. A polynomial with a degree of 0 is simply a constant function; with a degree of 1 is a line; with a degree of 2 is a quadratic; with a degree of 3 is a cubic, and so on. Historically, polynomial models are among the most frequently used empirical models for curve fitting.