v.

1. 计算
   We have to sum up the costs of production.

   我们得计算一下生产成本。

2. 总结
   Let's sum up our experience before going on.

   在继续做之前我们先来总结一下经验吧。

3. 总而言之（与 to 连用）
   To sum up, no matter the number of protests, pension reform must be carried out.

   总而言之，不管有多少反对的声音，年金改革势在必行。