In mathematics, Hermite's law of reciprocity, introduced by , states that the degree m covariants of a binary form of degree n correspond to the degree n covariants of a binary form of degree m. In terms of representation theory it states that the representations S<sup>m</sup> S<sup>n</sup> C<sup>2</sup> and S<sup>n</sup> S<sup>m</sup> C<sup>2</sup> of GL<sub>2</sub> are isomorphic.