Amount and number are both words that relate to quantity. The former refers to a singular item that can’t be counted. The latter requires a plural noun that can be counted. Let’s use stories to illustrate their use.
You serve at the local food pantry. Some months are lean; others are plentiful. When you’re asked to give the community board a report, you can provide fixed numbers from past months. You can’t do the same for the future. You have to tell the board, “The amount of food varies from month to month.” The type of food likely varies, too, explaining why every visitor to the pantry goes home with three to four jars of crunchy peanut butter.
Perhaps you would like to take some of that peanut butter home with you. You probably would if you were a CrossFitter. You need protein and lots of it. Bring on the peanut butter! In addition to protein, you need calories. You’re working out three to five times per week. You’ll soon be skin and bones rather than lean muscle if you don’t consume more food. You say, “I have to eat a certain number of calories per day.”
There you have it. A singular noun that can’t be counted requires an “amount.” A plural noun that can be counted needs a “number.”
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