A filter is designed to reject some substances, while permitting others to pass through.

VOA: special.2010.01.05

Ultimately, we need a filter or a lens to talk about then what is ultimately in control.

最终，我们需要一个视窗，一个镜头,来讨论什么是最终的控制者。

普林斯顿公开课 - 人性课程节选

What all of these channels have is what's called a selectivity filter, so this filter filters out the type of ion that's going to be allowed through.

这些离子通道都有的一部分,就是所谓的选择性过滤器，这个过滤器,会滤过允许穿过的离子。

麻省理工公开课 - 化学原理课程节选

The water filter costs little to make.

VOA: special.2009.06.22