Grimm's law (also known as the First Germanic Sound Shift) is a set of statements describing the inherited Proto-Indo-European (PIE) stops as they developed in Proto-Germanic (PGmc, the common ancestor of the Germanic branch of the Indo-European family) sometime in the 1st millennium BC. It establishes a set of regular correspondences between early Germanicstops and fricatives (see: Consonant) and the stop consonants of certain other 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:
#Proto-Indo-European voiceless stops change into voiceless fricatives.#Proto-Indo-European voiced stops become voiceless.#Proto-Indo-European voiced aspirated stops lose their aspiration and change into plain voiced stops.
The voiced aspirated stops may have first become voiced fricatives before hardening to the voiced unaspirated stops "b", "d", and "g" under certain conditions, however some linguists dispute this. See Proto-Germanic phonology.
Grimm's law was the first non-trivial systematic sound change to be discovered in linguistics; its formulation was a turning point in the development of linguistics, enabling the introduction of a rigorous methodology to historical linguistic research. The "law" was discovered by Friedrich von Schlegel in 1806 and Rasmus Christian Rask in 1818, and later elaborated (i.e. extended to include standard German) in 1822 by Jacob Grimm, the elder of the Brothers Grimm, in his book Deutsche Grammatik. Some scholars use the term Rask's-Grimm's rule.
English: wife, Proto-Germanic: wiban (from former gwiban), Old Saxon, Old Frisian: wif, Old Norse: vif, Danish, Swedish: viv, Dutch: wijf, Old High German: wib, German: weib
*Note: Some linguists dispute the origin of the word "wife". The current assumed root word is Proto-Indo-European *ghwíbh-.
This is strikingly regular. Each phase involves one single change which applies equally to the labials () and their equivalent dentals (), velars () and rounded velars (). The first phase left the phoneme repertoire of the language without voiceless stops, the second phase filled this gap but created a new one, and so on until the chain had run its course.
*Note: Some linguists dispute the origin of the word "scold" but *skwetlo is the current assumed root.
Similarly, *t did not become a fricative if it was preceded by *p, *k, or . The stop it was preceded by did fricativize, however. This is sometimes treated separately under the heading Germanic spirant law:
Ancient Greek: οκτώ (oktō), Latin: octō, Sanskrit: aṣṭan
*→h(w)t
English: night, Old High German: naht, Old Frisian, Dutch, German: nacht, Gothic: nahts
Greek: nuks, Latin: nox, Sanskrit: naktam
The most recalcitrant set of apparent exceptions to Grimm's Law, which defied linguists for a few decades, eventually received explanation from the Danish linguist Karl Verner (see the article on Verner's law for details).
The Germanic "sound laws", combined with regular changes reconstructed for other Indo-European languages, allow one to define the expected sound correspondences between different branches of the family. For example, Germanic (word-initial) *b- corresponds regularly to Latin *f-, Greek ', Sanskrit', Slavic, Baltic or Celticb-, etc., while Germanic *f- corresponds to Latin, Greek, Sanskrit, Slavic and Baltic p- and to zero (no initial consonant) in Celtic. The former set goes back to PIE * (faithfully reflected in Sanskrit and modified in various ways elsewhere), and the latter set to PIE *p- (shifted in Germanic, lost in Celtic, but preserved in the other groups mentioned here).
