Fewer vs. Less
Fewer and less both express a smaller quantity, but they're supposed to divide along one clean line: fewer for things you count individually (fewer apples, fewer people), less for things measured as a mass or continuum (less water, less time). The rule is simple to state and surprisingly inconsistently followed, including by native speakers, retailers, and even some professional style guides.
The core rule: count nouns vs. mass nouns
Fewer modifies plural count nouns — things you can individually enumerate: fewer books, fewer mistakes, fewer opportunities. Less modifies singular mass (noncount) nouns — things measured in bulk rather than counted one by one: less sugar, less traffic, less enthusiam. The test is whether you could meaningfully put a number in front of the noun (three books, yes — fewer) versus whether the noun resists being counted that way without a unit attached (you don't say 'three sugars' meaning grains of sugar, only 'three cups of sugar' — less).
The classic supermarket example
Grocery store express-lane signs reading '10 items or less' are the most commonly cited real-world violation of this rule, since 'items' is a countable plural noun and technically calls for 'fewer': 10 items or fewer. Some retailers and style-conscious grocers have switched their signage to 'fewer' specifically because of how often this exact example gets cited in grammar discussions, though 'less' on such signs remains extremely widespread and is rarely seen as a serious error by ordinary shoppers.
Amounts, distances, and time are treated as units, not counts
Expressions of time, money, distance, and weight are usually treated with less even though they might seem countable, because they're conceptualized as a single measured amount rather than as individually counted items: less than five minutes, less than $20, less than ten miles. The logic is that '$20' and 'five minutes' function as one unified quantity in these phrases, similar to how amounts of money or time take singular verbs in the subject-verb agreement rule — the countable-looking number is really describing a single measured span, not a set of discrete counted objects.
Why the rule gets broken so often in casual speech
In everyday spoken English, 'less' has been encroaching on 'fewer's' territory for a very long time — this isn't a new or purely modern decline, and some usage historians trace 'less' used with plural count nouns back centuries in English, even though 18th-century grammarians began actively promoting the strict fewer/less split around the same period the split-infinitive and other prescriptive rules were being formalized. That history complicates the idea that 'ten items or less' is simply sloppy modern usage; it's closer to a long-running natural tendency in English that formal grammar teaching has pushed back against for a long time.
Is this rule actually still enforced by editors?
Yes, in careful formal and edited writing, the fewer/less distinction remains actively maintained, and most professional copyeditors will still correct 'less' to 'fewer' before a plural count noun. In casual and conversational English, though, the substitution barely registers to most listeners, which creates the familiar split between what formal writing enforces and what everyday speech tolerates without complaint.
A related distinction: fewer vs. lesser
'Lesser' is a separate word entirely, used to mean 'smaller in importance or rank' rather than 'smaller in quantity': a lesser evil, a lesser-known author. It doesn't compete with fewer or less in the count/mass distinction at all — it's worth flagging mainly because its surface similarity to 'less' sometimes causes writers to reach for the wrong word when they actually mean a straightforward quantity comparison.
A quick mental test for uncertain cases
When unsure whether a noun is countable or a mass noun in a given context, try pluralizing it directly with a number: 'three problems' works (countable, use fewer), while 'three furnitures' doesn't work the way English is normally spoken (mass noun, use less). Some nouns can behave as either, depending on context — 'three cakes' (individual cakes, countable, fewer) versus 'less cake' (a mass of cake as a substance, less) — so the test should be applied to the specific sense intended in your sentence, not just the word in isolation.
How 18th-century grammarians shaped this rule
The formal fewer/less distinction is often traced to an 18th-century grammarian, Robert Baker, who suggested in 1770 that 'less' should be reserved for singular mass nouns, a suggestion that later grammar writers hardened into the fixed rule taught today. Unlike the split-infinitive myth, this rule isn't entirely invented from nothing — there was already a general tendency in English to favor 'fewer' with plural count nouns — but the absolute, no-exceptions version of the rule taught in schools is more rigid than how English speakers had actually used both words up to that point.
Money, percentages, and other tricky borderline cases
Percentages and statistical figures sometimes create genuine judgment calls: less than 50 percent of respondents (treating the percentage as a single measured proportion, hence less) versus fewer than half the respondents (treating 'half the respondents' as a count of individual people, hence fewer) — both are defensible depending on whether the writer is emphasizing a measured proportion or a headcount of individuals, illustrating that the rule sometimes requires a judgment about which framing the sentence intends rather than a purely mechanical check.
Fewer/less in comparative constructions with 'than'
The same rule applies consistently in comparative sentences: fewer than ten cars were sold (countable cars), less than an hour remained (a measured span of time), and mixing them up in either direction reads as the identical error regardless of whether 'than' is present — the presence of 'than' doesn't change which word is correct, only the overall comparative structure of the sentence.
A broader note on prescriptive rules that partially reflect real usage
Unlike a rule invented wholesale with no grounding in actual English (such as the split-infinitive prohibition), the fewer/less distinction reflects a real, if imperfect, tendency already present in the language before grammarians formalized it — which is part of why it's taken more seriously by usage authorities today than some other 18th-century prescriptions, even as everyday spoken usage continues to blur the line in exactly the contexts (like '10 items or less') that made the original distinction only a loose tendency rather than an absolute rule to begin with.
Fewer/less with negatives and questions
The rule holds the same way in negated and interrogative sentences: Are there fewer applicants this year? Isn't there less traffic on Sundays? Negation or question structure doesn't change whether the noun involved is countable or a mass noun, so the same count/mass test determines the correct word exactly as it would in a plain declarative sentence.
A note on how strictly to apply this rule in your own writing
For formal or professional writing where precision is valued — reports, academic papers, edited journalism — applying the fewer/less distinction consistently is worth the small extra attention it requires, since it remains one of the more visibly checked usage points among careful readers and editors. In casual writing or speech, deviating from the strict rule, especially in fixed or highly common phrases like '10 items or less,' is unlikely to draw real criticism from most audiences.
One more genuinely tricky case: 'less' with plural units treated as a single amount
Phrases like 'less than three years' or 'less than five dollars' use 'less' even though 'years' and 'dollars' are grammatically plural, because the phrase as a whole is functioning as one measured span or sum rather than a count of individually distinct years or dollar bills — the same logic covered earlier for time and money, restated here because it's the single most common place writers second-guess themselves even after learning the basic count/mass rule. Recognizing this pattern helps explain the difference between 'fewer than three cups of sugar' (counting whole cups as discrete units) and 'less sugar' (describing sugar as an uncountable substance) side by side.
Frequently asked questions
Is '10 items or less' actually wrong?
By the strict fewer/less rule, yes — 'items' is countable, so 'fewer' is technically correct. In practice it's an extremely common and widely tolerated usage, and most people don't perceive it as an error, though careful editors and some style guides still flag it.
Why does 'less than five miles' use less instead of fewer?
Because distance here is being treated as a single measured span rather than a count of individual miles — the same logic that treats amounts of time and money as singular, unified quantities rather than sets of discrete counted items.
Is this rule the same in British and American English?
The underlying rule is the same in both varieties, and both show similar rates of 'less' encroaching on 'fewer' in casual speech; neither variety treats this as a fundamentally different grammatical distinction.
Should I correct 'less' to 'fewer' if I see it in someone else's casual writing?
Only if you're specifically asked to edit for formal correctness — in casual or conversational contexts, correcting this is often perceived as needlessly pedantic given how common and generally accepted the 'less' substitution has become in everyday speech. In formal or professional editing contexts, though, applying the distinction consistently remains standard practice.