The grammar series: the difference between fewer and less
Remember how I went to Six Flags in May and got so tired that I couldn’t remember how to explain the different between fewer and less to J?
I figured I should probably settle that confusion. (Also, I realized I haven’t done a single grammar post since early June and that is just not okay.)
To get the ball rolling (as usual), here’s what AP Style has to say about fewer and less:
In general, use fewer for individual items, less for bulk or quantity.
Wrong: “The trend is toward more machines and less people.” (People in this sense refers to individuals.)
Wrong: “She was fewer than 60 years old.” (Years in this sense refers to a period of time, not individual years.)
Right: “Fewer than 10 applicants called.” (Individuals.)
Right: “I had less than $50 in my pocket.” (An amount.) Also right: “I had fewer than 50 $1 bills in my pocket.” (Individual items.)
AP Style has a lot of examples for this one, but they could clear up the definition by adding one memory trick: Fewer refers to things you can count. You can’t count Diet Coke, but you can count how many cans of Diet Coke you drank yesterday. (If you want to be really grammar-savvy, nouns you can count are count nouns, and nouns you can’t count are mass nouns.)

(In this case, we’re talking about Diet Coke as a mass quantity, rather than individual ounces or cans. Diet Coke is a mass noun.)

(But in this case, we’re talking about cans of Diet Coke as individual units. Cans of Diet Coke are count nouns.)
The one that seems confusing to me is the example, “She was fewer than 60 years old,” which is supposed to be less than 60 years old. You can count years, right? It didn’t make sense. So, I consulted my other grammar guru: Grammar Girl. She writes that there are some exceptions to the count nouns vs. mass nouns rule: time, money and distance. That’s why AP’s example is correct—it’s one of the exceptions.
Side note: Ever notice how express lanes in stores are for “10 items or less”? Ever since I learned fewer vs. less, that sign has bugged me every time. Then again, we’ve already established that I’m a little crazy.