labor

n. 工作,劳动,劳力,劳方
v. 苦干,劳动,分娩,阵痛
vi. 工作

It takes a lot of labor to build a railway.

修筑一条铁路要花费许多劳动力。

You needn't labor a point that is perfectly plain.

这点很明显，你用不着讲个没完。