fewer
determinera smaller number of things you can count
Fewer cars, fewer mistakes: things you can count.
Cars, mistakes and people take fewer in careful English. Water, time and money take less. (“Ten items or less” is common in shops.)
Quick answer
Use fewer with plural things you can count. Use less with amounts you cannot count, like time or money.

a smaller number of things you can count
Fewer cars, fewer mistakes: things you can count.
a smaller amount of something you cannot count
Less water, less time: you can't count it.
| Word | Type | Means | Example | Common mistake |
|---|---|---|---|---|
| fewer | determiner | a smaller number of things you can count | There are fewer cars on the road today. | |
| less | determiner | a smaller amount of something you cannot count | I drink less coffee now. |
determiner
Examples
There are fewer cars on the road today.
I made fewer mistakes this time.
Common mistake
Not: There were less people at the party.
Say: There were fewer people at the party.
In careful English, plural countable nouns take fewer.
determiner
Examples
I drink less coffee now.
We have less time than we thought.
Common mistake
Not: I have fewer money than last year.
Say: I have less money than last year.
Money is an amount you cannot count, so use less.
Read the sentence, then choose the word that fits.
Write or say two sentences, one with each word, in a real conversation.