Coefficient extraction ($[x_1^{a_1}\cdots x_n^{a_n}]P$)

Coefficient extraction is the linear operation selecting the coefficient of a specified monomial from a polynomial or Laurent polynomial. Multiplying by the inverse of that monomial reduces the operation to taking a constant term. The coefficient form of the Combinatorial Nullstellensatz expresses certain coefficient extractions as weighted sums of evaluations on a finite product set.