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. The total costs last month summed up to ￡ 1,300. 上个月的总费用高达1 300镑。
2. Her supposed wealth is a very small sum. 她可谓的财产只是很小的一笔钱。
3. To sum up, success results from hard work. 总而言之，成功是艰苦努力的结果。
英英解释
n.
1. a quantity of money
2. a quantity obtained by the addition of a group of numbers
3. the final aggregate
4. the choicest or most essential or most vital part of some idea or experience
5. the whole amount
6. the basic unit of money in Uzbekistan
7. a set containing all and only the members of two or more given sets v.
1. be a summary of
2. determine the sum of
