1
- a particular amount of money金额, 款项, 款子：
they could not afford such a sum.
他们付不起这样一笔款子。
2
- ( the sum of) the total amount resulting from the addition of two or more numbers, amounts, or items和, 总数：
the sum of two prime numbers.
两个素数之和。
2.1
- the total amount of something that exists总和：
the sum of his own knowledge.
他个人知识的总和。
3
- an arithmetical problem, especially at an elementary level算术题。
(summed, summing)with obj.
1- technical find the sum of (two or more amounts)〈技〉求…的和, 计算…的总数：
if we sum these equations we obtain X.
如果我们把这些方程式相加, 就能求得X.
1.1
- no obj.( sum to) (of two or more amounts) add up to a specified total共计, 总数达：
these additional probabilities must sum to 1.
这些额外的概率相加必然是1。
短语
in sum
- to sum up简言之; 总而言之：
this interpretation does little, in sum, to add to our understanding.
总而言之, 这个解释没有增进我们的理解。
词源
Middle English: via Old French from Latin summa 'main part, sum total', feminine of summus 'highest'.
短语动词
sum up
1
- give a brief summary of something总结, 概括：
Gerard will open the debate and I will sum up.
杰勒德将在辩论开始时发言, 而我将做总结。
1.1
- Law (of a judge) review the evidence at the end of a case, and direct the jury regarding points of law【律】（法官）总结性概述（指法官在案件结束时对证据进行回顾, 并在相关法律点上引导陪审团）。
sum someone/thing up
- express a concise idea of the nature or character of a person or thing对某人/某事作出简要概括：
selfish - that summed her up.
自私——这个词就可以将她概括了。