Think about the last time you heard the phrase, “There are less people here than last year.” Probably very recently, perhaps on a New Year’s Eve broadcast where a shivering rookie newscaster is commenting on the obvious decline in party attendance during a pandemic.
Now think of the last time you heard anyone say, “There is fewer water around since the start of the drought.” Probably never. Why? Because it sounds silly!
Actually, they both sound silly to a fluent English speaker. Countable nouns, nouns that can only be counted collectively as separate entities, are different from uncountable nouns. Each type of noun is paired with a different set of comparative modifiers according to certain rules. (Note to all physics nerds: we know that all tangible matter is countable, atomically speaking. Language is practical and subject to entirely different theories.) For example, for countable nouns, we use “fewer” rather than “less” because the word “few” points to something integral that can be counted. On the other hand, “less” is used for uncountable nouns, nouns that allow for degrees of measurement. For example, 6.1 oz. of water is less than 6.2 oz. of water.
When considering countable versus uncountable nouns, think of it this way: a hole can be larger or smaller in size and have differences in shape than other holes, but collectively, holes are strictly countable. A hole is a mathematical integer (another way of saying it’s countable); there is no such thing as a half a whole: six-and-a-half holes equals seven holes. Likewise, with uncountable nouns, there is no such thing as a piece of water (in the English language).
There are some problem words that grate on a curmudgeon’s ears in this regard, like “taxes.” Are taxes countable? Yes. Are taxes measurable in degrees? Yes. Argh! It all depends on context.
My brain swirls around these subjects as if it had nothing better to do. All I know is that the only time you would use “less” to describe “people” would be if you were talking about the disintegrated leftovers of a Soylent Green meal.
(Look it up, non-movie buffs!)