An astute follower of this blog, a Ms. Marsh of Frogmorton or thereabouts, comments with unconfined joy that the supermarket at which she purchases her vegetable marrows has erected signs at the express checkout counters that read “10 Items or Fewer.” The cause of her elation is not that she is able to whisk through the line in a speedier manner—but that some greengrocer-grammarian recognizes the difference between fewer and less.
Conventional rules prescribe that fewer should be used for numbers of things ("I want fewer than ten bottles of beer") and less for quantities and units of measure ("I want less beer" or "I want less than three pints of beer"). But nothing is as simple as it seems, even for a beer-soaked village grammarian. As the estimable Dictionary of Modern American Usage, by lawyer-lexicographer Bryan A. Garner, explains, “The exception in using fewer occurs when count nouns are so great as to render the idea of individual increments meaningless. So less is used correctly with time or money.” In other words, you should say a goal was achieved in “less than ten years” or that something will cost you “less than two dollars a day."
Sometimes it gets tricky, depending on inexpressible contextual factors. You might, quite correctly, rob four banks in “less than ten days,” but then you might, equally correctly (if leniently), be sentenced to “fewer than ten days in jail.”
The Bard of Buffalo Bayou took fewer than eleven moments to come up with the following suggestion for those supermarket signs:
If you’re quite sure
You’ve ten or fewer
Items on your shopping list,
Check out quickly—we insist!
For ten or less
There’s no express—
Get in line, for in this store
We believe that less is more.