There is an appropriate time to use the word few and an appropriate time to use the word less, but they are not interchangeable! It seems that everyone I talk to has the perversion of misusing these words. They have the spirit of the words under control, but they don't appear to realize that knowing the definition of the word is not enough to enable them to correctly apply them.

Examples of misuse:
  • There are less toes on my foot than before.
  • Canada has fewer area than Mexico and Russia combined.

  • The word less refers to the amount of something that you can't count, whereas the word fewer refers to the number of something that you can't count. Saying, "I have fewer toes than you!" makes sense because the word fewer is referring to the fact that the number of toes that I have is smaller than yours. It does not, then make sense to use the word fewer to modify words like milk, or soda because, although they can become plural, they aren't countable. It would just be wrong to say, "I have fewer soda than you!"

    So the general rule that gets to almost all cases of few vs. less use is this:

    If the noun you want to modify is plural and ends in the letter s, use the word few. If plural with no s, use less.