 Most languages have their vowels evenly and widely distributed over the chart, exhibiting a geometrically congruent vowel pattern. Here are some examples. Greenlandic has only three vowels, a high front vowel e, with a high back vowel counterpart u. Together, with the low central vowel a, they form a neat triangular pattern. However, such a small vowel system is the exception rather than the rule. Spanish, like many other languages of the world, has a system of five vowels. Whether two front vowels have their respective back vowel counterparts and a low central vowel completes the geometrical pattern. Our next example, Romanian, belongs to the majority of languages that have between five and seven vowels. Here a system of central vowels completes the pattern. These examples show that languages seem to develop geometrical vowel patterns. Each front vowel has a corresponding back vowel and vice versa. This phenomenon has become known as pattern congruity. But what about those vocali patterns where this is superficially not the case? Here is the case of German. The German tense monophthongs constitute an almost perfect pattern. One vowel, however, seems to disrupt the pattern, e, as in kése. It has no back counterpart. However, many German speakers realign the pattern and use e instead. They say kése.