-f ending of nouns

Q:

In my grammar class today, the students were wondering why the plural of chief is chiefs, yet the plural of most words ending in -f is -ves, such as thief --> thieves. Any explanations?

Jane C. Kirsch
jkirsch@gmu.edu

A:

It's true that many nouns ending in -f in the singular have a -ves ending for the plural.

Actually, however, there are three classes of nouns ending in -f, according to The Cambridge Grammar of the English Language (Cambridge University Press, 2002):

• Class 1 – Nouns that always change their endings to -ves. Examples are calf, elf, knife, leaf, life, loaf, self, sheaf, shelf, thief, wife and wolf.
  
• Class 2 – Nouns that may or may not change their endings to -ves. Examples are dwarf (dwarfs, dwarves), half, handkerchief, hoof, roof, scarf, and wharf.
  
• Class 3 – Nouns that don’t change their endings to -ves; they retain the -f ending and add just the plural -s. Examples are belief, chief, cliff, muff, oaf, photograph, proof, safe, tough, waif.

This reference notes that sometimes the voiced -ves, as in “handkerchief” occurs in speech in Class 2, but in writing—as in handkerchiefs and roofs—as Class 3.