The Umlaut Plurals
Umlaut plurals were words that did not have a characteristic suffix (as in book – books) to mark their plural form. These words used another way to indicate their plural status. For example: foot - feet, tooth - teeth, mouse - mice. These plurals did not characteristically change since the late Middle English. Common umlaut- plurals we also use today are feet, geese, lice, mice, men.