In mathematics, an irreducible polynomial is, roughly speaking, a non-constant polynomial that cannot be factored into the product of two non-constant polynomials. The property of irreducibility depends on the field or ring to which the coefficients are considered to belong. For example, the polynomial is irreducible if the coefficients 1 and -2 are considered as integers, but it factors as if the coefficients are considered as real numbers. One says "the polynomial is irreducible over the integers but not over the reals".