PolynomialQ

PolynomialQ[expr, var] yields True if expr is a polynomial in var, and False otherwise.

PolynomialQ[expr, {var1, …}] tests whether expr is a polynomial in the vari.

Examples

Test for polynomial:

PolynomialQ[x^2 + 2x + 1, x]
(* True *)

Not a polynomial:

PolynomialQ[1/x + x, x]
(* False *)

Please visit the official Wolfram Language Reference for more details.