Less and fewer are two of the most commonly-confused words in the English language. So many people have gone over the difference between these two words that I hesitated to write about it here. But I still see these used incorrectly in manuscripts that I edit, so we’d best go over it again.
Here’s the breakdown:
Fewer: Used when there is a smaller amount of a countable item (i.e. a number of individual items, something that could be pluralized—fewer leaves, fewer boxes, fewer people, fewer items).
Less: Used when there is a smaller amount of a non-countable item (i.e. a mass of a certain substance, something that shouldn’t generally be pluralized—less water, less sand, less angst, less stuff).
If you have trouble remembering which is which, remember: less already has the letter s in it twice, so it doesn’t need any more of them attached—don’t pluralize words that come after less. Fewer doesn’t have an s in it, so the word after it needs one.
Keep in mind:
—Usually, when people confuse these words, they use less when they should have used fewer. It’s very rare for anyone to use fewer when they should have used less.
—Sometimes people get confused on the countable vs. non-countable comparison. Sand, for instance, is composed of numerous tiny grains that could be counted, so it should be used with fewer, right? No, because we generally don’t pluralize sand. It would be “less sand,” but “fewer grains of sand.” Similar situations arise with words like hair, money, and more.
—To make matters even more confusing, some words can be used with both fewer and less, depending on the context. For example, the word substance:
The second book just had less substance to it.
The police confiscated fewer substances from the drug dealer than expected.
In the first example, substance is being used in an abstract, uncountable sense, so we use less. In the second example, it is used to refer to a concrete, countable amount of specific items, so we use fewer.