Editing Indo-European ablaut (section)

==Ablaut and vowel gradation==
{{further|Apophony}}
Vowel gradation is any vowel difference between two related words (such as ''ph'''o'''tograph'' [ˈf'''oʊ'''təgrɑːf] and ''ph'''o'''tography'' [f'''ə'''ˈtɒgrəfi]) or two forms of the same word (such as ''m'''a'''n'' and ''m'''e'''n''). The difference does not need to be indicated in the spelling. There are many kinds of vowel gradation in English and other languages, which are discussed generally in the article [[apophony]]. Some involve a variation in vowel length (quantitative gradation: ''ph'''o'''tograph'' / ''ph'''o'''tography'' shows reduction of the first vowel to a [[schwa]]), others in vowel coloring (qualitative gradation: ''m'''a'''n'' / ''m'''e'''n'') and others the complete disappearance of a vowel (reduction to zero: ''could n'''o'''t'' → ''couldn't'').

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 ''r'''i'''de'', ''r'''o'''de'', ''r'''i'''dden'', or ''fl'''y''''', ''fl'''ew''''', ''fl'''ow'''n''. For simply learning English grammar, it is enough to note that these verbs are [[irregular verb|irregular]], but understanding why they have unusual forms that seem irregular (and indeed why they are actually perfectly regular within their own terms) requires an understanding of the grammar of the [[Reconstructed language|reconstructed proto-language]].

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|Germanic umlaut]] (''m'''a'''n'' / ''m'''e'''n'', ''g'''oo'''se'' / ''g'''ee'''se'', ''l'''o'''ng'' / ''l'''e'''ngth'') or the results of modern English word-stress patterns (''m'''a'''n'' / ''wom'''a'''n'', ''ph'''o'''tograph'' / ''ph'''o'''tography''). Confusingly, in some contexts, the terms 'ablaut', 'vowel gradation', 'apophony' and 'vowel alternation' are used synonymously, especially in [[wikt:synchronic|synchronic]] comparisons, but [[historical linguistics|historical linguists]] prefer to keep 'ablaut' for the specific Indo-European phenomenon, which is the meaning intended by the linguists who first coined the word.