I’m always pretty meticulous about my use of “fewer” and “less” but was surprised today to read that usage guru Bryan Garner is almost permissive (and at least understanding) of the tendency to mix them up, saying that calling the common mixup an error is a bit strong. He goes on to explain that grocery stores have been largely responsible for widespread substitution of “less” for “fewer.” This will come as no surprise to any usage-minded folk who avoid the express lane at their store if only to avoid tacitly consenting to the phrase “15 items or less.”
So, maybe this is a losing battle for those who favor traditional usage, but I think it’s interesting to peek into what the traditional usage dictates.
“Fewer” is appropriate when writing or speaking about plural nouns; so you have fewer marbles and teeth and Persian rugs. “Less” is appropriate when writing about units of measurement, singular nouns, or (quoting Garner here) “count nouns so great as to render the idea of individual increments meaningless.” So you’ll write about less water (a singular, un-numerable noun), less than X ounces of something (a unit of measure), and less money. This last case is a little tricky, as you could easily talk about having fewer dollar bills or coins. The idea is that when you’re comparing vague or uncounted, collective things, it’s usually appropriate to use “less,” while when comparing countable finite items, “fewer” is better.
Even with those rules in place, Garner concedes that it’s sometimes a tough call. Comparing percentages can be dicey, for example, because in some cases either “fewer” or “less” could work. In such cases, it may be best to choose “less” as the less formal option.
If you’re a grammar and usage nerd, Garner’s book really is a must-have. I wrote about it a few weeks ago and have probably used it on a nearly daily basis ever since, sometimes to guide my writing and sometimes just for fun (once or twice even to settle a bet). I think I’ve made
less fewer mistakes as a result.