"Number" is used for things that can be counted individually; "amount" is used for things that cannot be counted (masses or quantities).
Noun. The quantity of countable, separable things. Used with plural countable nouns.
The number of students in the class is twenty-five.
El numero de alumnos en la clase es veinticinco.
A large number of people attended the concert.
Un gran numero de personas asistio al concierto.
The number of cars on this street has increased.
El numero de autos en esta calle ha aumentado.
Noun. The quantity of something uncountable or massive. Used with uncountable nouns like water, time, money, information.
The amount of water we waste every day is shocking.
La cantidad de agua que desperdiciamos cada dia es alarmante.
She paid a large amount of money for that painting.
Ella pago una gran cantidad de dinero por esa pintura.
The amount of time needed for this project is uncertain.
La cantidad de tiempo necesaria para este proyecto es incierta.
Common mistake
Very common error: "The amount of people at the party was huge." is wrong. People are countable (you can count individual persons). Correct: "The number of people at the party was huge." Parallel rule to less/fewer: "amount" goes with uncountables (water, money, time), "number" goes with countables (people, cars, books).
Trick to remember it
Same trick as less/fewer: if you can count things one by one, use "number". If it is a mass or flow that does not separate into individual units, use "amount". People, cars, mistakes = number. Water, money, time, information = amount.
Quick rule
Number + countable nouns (people, objects). Amount + uncountable nouns (water, time, money).
Did you know?
"A number of" (indefinite article) means "several" or "some" and takes a plural verb: "A number of students have questions." But "the number of" (definite article) treats the group as singular: "The number of students has increased." Same pattern with "the amount of": always singular.
Exercise 1 · Pick the right one
The _____ of mistakes in this document is unacceptable.
Exercise 2 · Pick the right one
She was surprised by the _____ of information available online.
Exercise 3 · Form the word
Number + countable nouns (people, objects). Amount + uncountable nouns (water, time, money).
Very common error: "The amount of people at the party was huge." is wrong. People are countable (you can count individual persons). Correct: "The number of people at the party was huge." Parallel rule to less/fewer: "amount" goes with uncountables (water, money, time), "number" goes with countables (people, cars, books).
Same trick as less/fewer: if you can count things one by one, use "number". If it is a mass or flow that does not separate into individual units, use "amount". People, cars, mistakes = number. Water, money, time, information = amount.
Bryan López
Founder of SpeakUP Academy