One reduces uncountable things, the other reduces countable things.
Adjective or adverb. Used with uncountable nouns or quantities in general. Equivalent to 'not as much'.
Try to eat less sugar.
Intenta comer menos azúcar.
I have less time than I thought.
Tengo menos tiempo del que pensaba.
She sleeps less than eight hours a day.
Ella duerme menos de ocho horas al día.
Adjective. Used only with plural countable nouns. Equivalent to 'not as many'.
There are fewer students this year.
Hay menos estudiantes este año.
He makes fewer mistakes now.
Él comete menos errores ahora.
Fewer people voted in this election.
Menos personas votaron en esta elección.
Common mistake
Using 'less' with countable nouns. Wrong: "There are less cars on the road today." (correct: fewer cars)
Trick to remember it
If you could use 'few' (for countables), use 'fewer'. If you could use 'little' (for uncountables), use 'less'. The pairs are: few/fewer and little/less.
Quick rule
Can you count the noun (people, cars, mistakes)? Use 'fewer'. Cannot count it (time, money, traffic)? Use 'less'.
Did you know?
US supermarket express lanes often say '10 items or less', but grammarians insist it should be 'fewer'. This debate has existed since the 1970s. In everyday informal speech, 'less' with countable nouns is widely accepted — in writing, 'fewer' is the safer choice.
Exercise 1 · Pick the right one
I need to drink _____ coffee. It makes me anxious.
Exercise 2 · Pick the right one
_____ people attended the concert than expected.
Exercise 3 · Form the word
Can you count the noun (people, cars, mistakes)? Use 'fewer'. Cannot count it (time, money, traffic)? Use 'less'.
Using 'less' with countable nouns. Wrong: "There are less cars on the road today." (correct: fewer cars)
If you could use 'few' (for countables), use 'fewer'. If you could use 'little' (for uncountables), use 'less'. The pairs are: few/fewer and little/less.
Bryan López
Founder of SpeakUP Academy