Use amount to refer to a quantity. Use number to refer to people or things that can be counted.
- All states have a special court designed to handle disputes where only a small amount of money is involved.
- Ryan filled the briefcase with a large number of hundred-dollar bills.
- An enormous amount of energy was exerted by a small number of people.
- "Number is regularly used with plural count nouns to indicate an indefinite number of individual items; its use is not disputed.
"Amount is most frequently used with singular mass nouns. . . .
"Amount is also used with plural count nouns when they are thought of as an aggregate:
- . . . who wrote the U.N. that he'd be glad to furnish any amount of black pebbles. --New Yorker, 20 Sept. 1952This less common use of amount is sometimes called incorrect, but the critics bring forward no cogent reason for condemning it. The use is well established in general prose."
- . . . the high amount of taxes. --Harper's Weekly, 29 Sept. 1975
- $6.5 billion: Amount of advertising dollars spent on pre-buys for the fall season. --Time, 7 June 1999
(Merriam-Webster's Concise Dictionary of English Usage, Merriam-Webster, 2002)
- "Use amount with singular mass nouns (an amount of money; the amount of love), and use number with plural count nouns (the number of castles; a number of sophomores). Common and Vulgar English frequently use amount with plural count nouns (a huge amount of children on the playground), and repeated exposures to that usage often blur the Standard models for us. There are also instances where plural count nouns are treated as representing those items in mass and hence usable with amount (He contracted for an enormous amount of apples). In speech such a use might go almost unnoticed, but Edited English would most likely change it to number or find an entirely different way to say it."
(Kenneth G. Wilson, "amount, number," The Columbia Guide to Standard American English, 1993)
(a) Expect a certain _____ of madness when you marry someone with pets.
(b) A great _____ of pets can drive you mad.