复数： vapours

It is effective , but mercury vapour is extremely toxic .

这种提取方法效率很高，可是遗留下来的水银蒸气含有剧毒。

Their method exploits the fact that water vapour changes the speed at which radar waves travel though air .

他们的方法是对水蒸汽改变雷达波穿过空气速度的实际情况加以运用。

The user inhales the vapour .

吸毒者吸入鸦片烟。

But one problem was that what appeared to be real demand may have been partly vapour .

但有一个问题：那些看似真实的需求或许已经“蒸发”掉一部分。

On the other , water vapour is transparent , whereas clouds reflect light .

另一方面，水蒸气是透明的，但云却可以反射光线。