拉格朗日插值法可以找到一个多项式，其恰好在各个观测的点取到观测到的值。这样的多项式称为拉格朗日（插值）多项式。数学上来说，拉格朗日插值法可以给出一个恰好穿过二维平面上若干个已知点的多项式函数。(Lagrange interpolation can find a polynomial, which happens to take the observed value at each observation point. Such polynomials are called Lagrange polynomials. Mathematically, Lagrange interpolation can give a polynomial function that happens to cross just a few known points in a two-dimensional plane.)