,
where the coefficients aij are elements of some ring. Polynomials in 3 or more variables are defined similarly.

When we substitute a value b into the polynomial f(x) then we get an actual number as output. This number is the value anbn + an − 1bn − 1 + ... + a2b2 + a1b + a0. This process is called "evaluating the polynomial at b".

Some algorithms are said to perform in polynomial time. There are algorithms which can factor polynomials in an amount of time that is a polynomial nk.