任务书的英文：
requirement

参考例句：

The prime contractor and the software subcontractor agree to their commitments to each other.
主签约人和子签约人互相接受他们的任务书。

requirement是什么意思：
n. 需要；必需品；要求；必要条件；规定

Is the requirement compulsory?
必须按这个需求做吗？

In practice, this will often require a prioritization of your job requirements.
实务上，这往往需要重新调整工作的优先顺序。

All systems requiring accurate timing will require a crystal.
所有需要精确定时的系统都要用晶体。

Excision of an obnoxious passage was required.
有一段引起反感的文字必须删掉。

require or ask for as a price or condition.
要求或者请求价格或者社会地位。