Searching Google for “less than” brings you ska bands, 80s novels and some obscure Andy Dick sitcom. But search for “fewer than,” less-than’s bookish cousin, and you get queries clearly demonstrating that no one else knows how/when they’re supposed to use “fewer” either.
The basic rule is: If you can count it, use fewer; if you can’t, less. Example:
There are fewer jelly beans in this jar than that jar.
I have less interest in how many jelly beans there are than in how to get them into my face.
The can-you-count-it rule can occasionally returns different results for seemingly the same subject. EG Time. I have less time to do this than I need. (The object, time, is indefinite.) I spent fewer hours on the project than I thought I’d need. (You thought you needed a certain — definite — number of hours, you used fewer than that.) Also consider something like sand: There’s less sand in a minute timer than a 3-minute timer. VS I counted the grains of sand in each timer, there are indeed fewer in the minute one.
Similar questions might arise when determining whether to use “farther” or “further.” According to Webster’s:
Farther and further have been used more or less interchangeably throughout most of their history, but currently they are showing signs of diverging…. A polarizing process appears to be taking place in their adjective use. Farther is taking over the meaning of distance <the farther shore> and further the meaning of addition <needed no further invitation>.
Imagine: physical distance = farther. (Get it? Far?)
But that’s if you’re keen to keep up with current linguistic trends. Webster’s says it’s historically kosher to use further and farther interchangeably when distance is involved, whether that distance is literal (It’s fa/urther from the subway), or metaphorical (He has fa/urther to go before he’ll be ready). But when there’s no notion of distance, further is always your man: This matter needs to be further explored; Further, you have more studying to do.
Got any questions of your own about esoteric adjectives and adverbs? Feel free to send me your queries and I’ll Google the answers for you.