that which infringes if later, anticipates if earlier

A rule stating the equivalence between two tests under patent law (i.e., the test of infringement of a patent and the test of anticipation in the prior art to invalidate a patent). If the claim of a patent is literally infringed by a prior art reference, then the claim is anticipated by that prior art reference and, therefore, is unpatentable. Note that there cannot be anticipation of a claim by equivalents.