From a diachronic (historical) perspective, the distinction between ablaut and umlaut is very important, particularly in the Germanic languages, as it indicates where and how a specific vowel alternation originates. It is also important when taking a synchronic (descriptive) perspective on old Germanic languages such as Old English, as umlaut was still a very regular and productive process at the time. When taking a synchronic perspective on modern languages, however, both processes appear very similar. For example, the alternations seen in "sing/sang/sung" and "foot/feet" both appear to be morphologically conditioned (e.g. the alternation appears in the plural or past tense, but not the singular or present tense) and phonologically unpredictable.