High Quality Content by WIKIPEDIA articles! Grimm`s law (also known as the First Germanic Sound Shift or the Rask`s-Grimm`s rule), named after Jacob Grimm, is a set of statements describing the inherited Proto-Indo-European (PIE) stop consonants as they developed in Proto-Germanic (the common ancestor of the Germanic branch of the Indo-European family) in the 1st millennium BC. It establishes a set of regular correspondences between early Germanic stops and fricatives and the stop consonants of certain other centum Indo-European languages (Grimm used mostly Latin and Greek for illustration). As it is presently formulated, Grimm`s law consists of three parts, which must be thought of as three consecutive phases in the sense of a chain shift: