Amount, when used as a noun, describes a quantity of uncountable nouns, such as air, water, or time. When used as a noun, number signifies a quantity of countable nouns, such as trees, cities, or papers.

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When is amount used?

When used a noun: For instance, We did not have sufficient amount of time to visit the park. As a verb, amount is used with to (amount to); it describes an accumulation of something. For instance, My bill amounted to $400.

When is Number used?

When used as noun: For instance, I have to review a number of research papers today. Number is also used as a verb when you want to give a serial number to something or to count something that is typically large in numbers. For instance, All the seats in the classroom are numbered.

Tips to Remember

Incorrect: We noted the amount of atoms present in 100g of sodium chloride. Since ‘atom’ is a countable noun, using the word amount makes the sentence unidiomatic. The right word to use is number, and the correct sentence is: Correct: We noted the number of atoms present in 100g of sodium chloride.