In historical linguistics, the German term Grammatischer Wechsel ("grammatical alternation") refers to the effects of Verner's law when viewed synchronically within the paradigm of a Germanic verb. Historical linguistics (also diachronic linguistics or comparative linguistics) is primarily the study of the ways in which languages change over time, by means of examining languages which are recognizably related through similarities such as vocabulary, word formation, and syntax, as well as the surviving records of ancient languages. ... Verners law, stated by Karl Verner in 1875, describes a historical sound change in the proto-Germanic language whereby voiceless fricatives *f, *þ, *s and *x, when immediately following an unstressed syllable in the same word, underwent voicing and became respectively *b, *d, *z and *g. ... The Germanic language family is one of the language groups which resulted from the breakup of Proto-Indo-European. ...

According to Grimm's law, the Proto-Indo-European (PIE) voiceless stops *p, *t and *k usually became Proto-Germanic *f, *þ (dental fricative) and *x (velar fricative). Karl Verner identified the principle that these instead become the voiced stops *b, *d and *g if they were word-internal and immediately preceded by an unstressed vowel in PIE. Furthermore, PIE *s, which usually came into Germanic unchanged, became *z in this position; Proto Germanic *z later became Germanic *r. Grimms law (also known as the [First] Germanic Sound Shift; German: Erste Deutsche (Germanische) Lautverschiebung) was the first non-trivial systematic sound change ever to be discovered; its formulation was a turning-point in the development of linguistics, enabling the introduction of rigorous methodology in historical linguistic research. ... Proto-Indo-European Indo-European studies The Proto-Indo-Europeans are the hypothetical speakers of the reconstructed Proto-Indo-European language, a prehistoric people of the late Neolithic and early Bronze Age. ... Phoneticians define phonation as use of the laryngeal system to generate an audible source of acoustic energy, i. ... A stop, plosive or occlusive is a consonant sound produced by stopping the airflow in the vocal tract. ... Karl Adolf Verner (1846 - 1896) was a Danish linguist. ... Phoneticians define phonation as use of the laryngeal system to generate an audible source of acoustic energy, i. ...

Consequently, four pairs of consonants emerged, each pair representing a single PIE phoneme. Further developments gave the following patterns in the earliest stages of English, German and Dutch. It is mainly in the dentals that these languages show significant differences in the patterns of grammatischer Wechsel.

(In Old English the fricatives took the voiced allophones /ð/, /v/ and /z/ when they were word internal; see: Pronunciation of English th. In Old High German the stops were moved according to the High German consonant shift. In Dutch, the ideocyncracies of this shift mean that Dutch (like German) experiences the shift þ→d but (like English) does not experience the shift d→t; thus the dental variety of grammatischer Wechsel is eliminated in Dutch by the normal operation of sound laws.) In English, the digraph <th> represents two phonemes, the voiced dental fricative /ð/ (as in this) and the voiceless dental fricative /θ/ (thing). ... In historical linguistics, the High German consonant shift or Second Germanic consonant shift was a philological development (sound change) which took place in the southern dialects of German in several phases, probably beginning between the 3rd and 5th centuries AD, and was almost complete before the earliest written records in...

Grammatischer Wechsel is the phenomenon that a verb which in PIE had a stem ending in one of these phonemes displays a differing reflex in different parts of the paradigm, a result of the movable nature of stress in PIE. This only affects West Germanic strong verbs. The regular pattern is that Grimm's law forms are found in the present stem and in the preterite singular, while Verner's law forms are found in the preterite plural and in the past participle. In the Germanic languages, strong verbs are those which mark their past tenses by means of ablaut. ...

A process of levelling has meant that there are only few examples of this in the modern languages. In East and North Germanic, this levelling was almost complete before the earliest records, though Gothic and Old Norse did have traces of Grammatischer Wechsel. In Old English, too, the levelling had already begun to the extent that in some verbs the preterite singular had taken the consonant of the preterite plural. The only surviving example in Modern English is was:were, but a trace can also be seen in the adjective forlorn, which reflects the old participle of the verb to lose. Likewise Modern German has lost most of its examples by levelling, but d:t can be observed in verbs like leiden, litt, gelitten ("to suffer") or h:g in ziehen, zog, gezogen ("to pull").

Some examples:

Original /*p/

Old English hebban - hōf hōfon hafen ("to lift" cf. heave)

Original /*t/

Old English: cweþan (cwiþþ) cwæþ - cwǽdon cweden ("to say": cf.quoth)

Old English: sēoþan (sīeþþ) sēaþ - sudon soden ("to boil" cf. seethe)

Modern German: schneiden - schnitt geschnitten ("to cut")

Original /*k/

Middle High German: zîhen zêch - zigen gezigen ("to pull")

Old English: þeon (þīehþ) þāh - þigon þigen ("to prosper" cf. German gedeihen)

Original /*s/

Old English cēosan (cīest) cēas - curon coren ("to choose")

Old English frēosan (frīest) frēas - fruron froren ("to freeze")

NB. The consonant change in certain weak verbs which typically goes along with the Rückumlaut phenomenon (think:thought, German denken:dachte) is not caused by grammatischer Wechsel, but by a later development in Germanic. In Germanic languages, weak verbs are those verbs that form their preterites and past participles by means of a dental suffix, an inflection that contains a /t/ or /d/ sound. ... Ä ä Ö ö Ü ü The term umlaut is used for two closely related notions: a special kind of vowel modification and a particular diacritic mark. ...