Fewer means a smaller number of countable things. When you have fewer apples than your friend, you can count exactly how many each of you has: maybe you have three and your friend has five. When there are fewer students in class today, you could count the empty desks.

The key is that fewer works with things you can count individually: fewer books, fewer questions, fewer minutes, fewer chances. This makes it different from less, which describes amounts you can't count separately, like less water, less time, or less trouble.

You might notice fewer cars on the road during summer vacation, eat fewer cookies than you wanted, or have fewer spelling words to memorize this week. Signs that say “10 items or less” at the grocery store are sometimes called incorrect by grammar experts: they say it should be “10 items or fewer” because you can count items one by one.

People sometimes mix up fewer and less, but remembering the counting rule helps keep them straight. If you can count it (five dogs, twelve pencils, twenty problems), use fewer. If you measure it as a whole amount (more patience, less noise, more courage), use less.