Then, around the 7th Century, a vowel shift took place in Old English pronunciation (analogous to the Great Vowel Shift during the Early Modern period) in which vowels began to be pronouced more to the front of the mouth. The main sound affected was "i", hence its common description as "i-mutation" or "i-umlaut" (umlaut is a German term meaning sound alteration). As part of this process, the plurals of several nouns also started to be represented by changed vowel pronunciations rather than changes in inflection. These changes were sometimes, but not always, reflected in revised spellings, resulting in inconsistent modern words pairings such as foot/feet, goose/geese, man/men, mouse/mice, as well as blood/bleed, foul/filth, broad/breadth, long/length, old/elder, whole/hale/heal/health, etc.