Grimm's Law

Grimm's law describes a regular, systematic set of consonant shifts that separates the Germanic languages, including English, German and the Scandinavian languages, from the other branches of the Indo-European family. It shows, for example, that where Latin and Greek preserve an original p, t or k sound, the Germanic languages regularly show f, th or h instead. Jacob Grimm set the pattern out as a general law in the 1822 second edition of his Deutsche Grammatik, building on an earlier, narrower observation by the Danish scholar Rasmus Rask, and it became the model for the sound law method that has driven historical linguistics ever since.