Amount vs Number vs Quantity: Countable, Uncountable, and Formal Usage

The textbook rule is useful but incomplete: number normally goes with countable nouns, while amount normally goes with uncountable nouns.

So a large number of applicants and a large amount of information are safe choices. Quantity is broader and often more formal: a substantial quantity of water; quantities of documents.

Why “amount of people” is controversial

You will hear it, especially when a group is treated as a mass, but careful edited prose still strongly prefers number of people. Register therefore matters.

Do not confuse the noun with the measurement

The number of errors fell means the count fell. A number of errors were found means several errors were found. Subject–verb agreement changes with the structure.

For the countability system underneath these choices, review countable and uncountable nouns and fewer vs less.