n.

1. 不纯；不洁[U][C]
2. 不道德；淫猥；渎神[U][C]
3. 杂质；不纯之物；不洁之物[C]
   Filtering the water removed some of its impurities.

   把水过滤一下除去了一些杂质。

n.

1. the quality or condition of being impure.
2. a constituent which impairs the purity of something.
3. Electronics  a trace element deliberately added to a semiconductor; a dopant.