Do you you remember the rules?
knife - , thief - , wife - , calf - , leaf - , wolf - , shelf - , half - , life - , loaf -
However, here are some exceptions to the rule:
chief - , handkerchief - , proof - , safe - , cliff - , roof -

Do you remember the rule concerning -y? Then you shouldn't have any problems here:
toy - , boy - , day -
story - , hobby - , family -

Do you remember what you have to do if the noun ends with -o?
volcano - , motto - , echo - , tomato - , potato - , hero -
kilo - , photo - , piano - , radio -


Do you know the irregular plural forms of the following words?
woman - , man - , gentleman - , policeman -
tooth - , goose - , foot -
salmon - , sheep - , aircraft - , cattle -
child - , ox -
louse - , mouse -
analysis - , crisis - , thesis -
erratum - , bacillus -