thieves
以-f或-fe结尾的名词，一般将-f，-fe去掉，加-ves。如：wife-wives, wolf-wolves, calf-calves.
这类名词还有：life, knife, self, shelf, leaf, thief, sheaf, half等。
名词scarf, wharf, hoof, handkerchief的复数形式或加-s或去掉-f加-ves，即scarfs或scarves, wharfs或wharves, hoofs或hooves, handkerchiefs或handkerchieves。
也有些以-f或-fe结尾的名词只加-s。如：cliff-cliffs, belief-beliefs, safe-safes, roof-roofs, chief-chiefs等。
