Troublesome pairs: "less than" v. "fewer than"

Some usage authorities and style guides insist that fewer than should only be used when you’re talking about things that you can count, such as marbles, people, or humpback whales, and that less than must be reserved for amounts that aren’t in distinct units. For example, you can say “I used fewer cups of flour” (you can count the cups) or “I used less flour,” (you can’t count flour). That distinction is all well and good as a personal preference, but it shouldn’t be elevated to the status of Iron-Clad Rule™ when it isn’t one.

It is true that you shouldn’t use fewer for non-countable amounts (and it’s pretty easy for most people to recognize that “I have fewer courage than you,” is just wrong). Less, on the other hand, can be applied to both countable and non-countable amounts. According to Merriam-Webster’s Concise Dictionary of English Usage, we have written evidence that people have been using less for countable things since about 888 A.D.

It might help to look at it in a little Venn diagram:

Let’s think about the general category of “Stuff,” and the smaller sub-category of “Stuff you can count.” The larger category of “Stuff” includes both the countable and non-countable—apples, sand, geckos, intelligence, marbles, molybdenum, politicians, and so forth—and the adjective less can be applied to all of it. Within the sub-category of “Stuff you can count”—from our previous list, the apples, geckos, marbles, and politicians—you can use both less and fewer.

In some cases, less might sound better than fewer. For example, I think “There were less than 10 people at the party” sounds better than “There were fewer than 10 people at the party.” But that’s entirely subjective. Both are entirely correct, so in those cases, use your ear.