An example of ablaut in English is the strong verb sing, sang, sung and its related noun song, a paradigm inherited directly from the Proto-Indo-European stage of the language.
[1][2] The phenomenon of Indo-European ablaut was first recorded by Sanskrit grammarians in the later Vedic period (roughly 8th century BCE), and was codified by Pāṇini in his Aṣṭādhyāyī (4th century BCE), where the terms guṇa and vṛddhi were used to describe the phenomena now known respectively as the full grade and lengthened grade.
[3][4][5] In the context of European languages, the phenomenon was first described in the early 18th century by the Dutch linguist Lambert ten Kate, in his book Gemeenschap tussen de Gottische spraeke en de Nederduytsche ("Common aspects of the Gothic and Dutch languages", 1710).
[a] In particular, the 17th-century grammarian Schottelius had used the word negatively to suggest that German verbs lacked the sophistication of the classics,[b] but there is no hint of this disdain in Grimm or in modern scholarly usage.
For the study of European languages, one of the most important instances of vowel gradation is the Indo-European ablaut, remnants of which can be seen in the English verbs ride, rode, ridden, or fly, flew, flown.
Ablaut is the oldest and most extensive single source of vowel gradation in the Indo-European languages and must be distinguished clearly from other forms of gradation, which developed later, such as Germanic umlaut (man / men, goose / geese, long / length) or the results of modern English word-stress patterns (man / woman, photograph / photography).
A classic example of the five grades of ablaut in a single root is provided by the different case forms of two closely related Greek words.
To understand, one must be aware that there were a number of sounds that were consonants in principle but could operate in ways analogous to vowels: the four syllabic sonorants, the three laryngeals and the two semi-vowels: When u and i came in postvocalic positions, the result was a diphthong.
However, not every PIE syllable was capable of forming a zero grade; some consonant structures inhibited it in particular cases, or completely.
However, some argue controversially that the e-grade could sometimes be replaced by an a-grade without the influence of a laryngeal, which might help to explain the vowels in class 6 Germanic verbs, for example.
Although PIE had only this one, basically regular, ablaut sequence, the development in the daughter languages is frequently far more complicated, and few reflect the original system as neatly as Greek.
For example, in Germanic, syllabic sonorants acquired an epenthetic -u-, thus converting the original zero grade to a new "u-grade" in many words.
For the English-speaking non-specialist, a good reference work for quick information on IE roots, including the difference of ablaut grade behind related lexemes, is Watkins (2000).
An example of ablaut in the paradigm of the noun in PIE can be found in *pértus, from which the English words ford and (via Latin) port are derived (both via the zero-grade stem *pr̥t-).
Examples in modern English are the following: It was in this context of Germanic verbs that ablaut was first described, and this is still what most people primarily associate with the phenomenon.