quantity 书面用词，指事物的总量和总数量，侧重大批计量，含准确测量的意味。
amount 普通用词，与quantity近义，但强调整体，指把所有数量、重量及度量归并在一起得出的总数。
number 普通用词，指人或物的数目，强调数的概念。
sum 普通用词，指简单加算的结果。
参考例句
1. He numbered 5 cars last year. 去年他就拥有五部轿车了。
2. Hope I can roll a decent)number. 希望我能卷一相当好的）数目。
3. Would you tell me your phone number? 你能告知我你的电话号码吗？
英英解释
n.
1. the property possessed by a sum or total or indefinite quantity of units or individuals
2. a concept of quantity derived from zero and units
3. a short theatrical performance that is part of a longer program
4. a numeral or string of numerals that is used for identification
5. the number is used in calling a particular telephone
6. a symbol used to represent a number
7. one of a series published periodically
8. a select company of people
9. the grammatical category for the forms of nouns and pronouns and verbs that are used depending on th
10. an item of merchandise offered for sale
11. a clothing measurement v.
1. add up in number or quantity
2. give numbers to
3. enumerate
4. put into a group
5. determine the number or amount of
6. place a limit on the number of
