(1) When ablaut is a regular feature of a language's grammar, it is often called vowel gradation.(2) It is the relationship between phonemic pitch and the nature of ablaut in standard Lithuanian which makes this clear.(3) There are various categories of this: rhyming, exact and ablaut (vowel substitution).(4) an ablaut series(5) The Proto-Indo-European phonetics was not stable at all: ablauts (vowel interchanges), assimilations, many different consonant processes at the end of the word.(6) You can't even distinguish between the preterite and participle Germanic ablauts of English.
