 Ablaut is a system of regular vocaliic variation in proto-Indo-European that has far-reaching consequences in all of the modern Indo-European languages. The term ablaut was coined in the 19th century by Jacob Grimm and it denotes a root vowel change that gives a word a new grammatical function. For example, verbs in their present tense form that exhibit the vowel e could be turned into the past tense formed by a change from e to a. In Indo-European, the common ancestor language to most European languages such changes systematically express differences such as present versus past tense or singular versus plural. This feature is still used in many Indo-European languages. For example, in English verbs where the past tense is formed by a change from short e to short a as in drink, drank, sit, sat or swim, swim or similarly in German present versus past tense roots such as drink, drank or swim, schwamm. Ablaut must be distinguished from other forms of vocaliic gradation which developed later such as Germanic umlaut or the results of English word stress patterns.