(2) 引导非限制性定语从句

在非限制性定语从句中，as作为关系代词代替整个主句，在从句中多作主语，as从句中的系动词be常常可以省略。as引导的从句位置比较灵活，可以位于主句之前、之中或主句之后。一般用逗号与主句隔开，可译为“如”、“正如……一样”、“根据”、“这”等。如：

* As described above, the laser beam is much more powerful than other light beams.

如上所迷，激光束比其他光束要强烈的多。

* As is noted in the preceding section, two essential elements of any computer are a memory and a processor.

正如前一节指出的那样，任何计算机的两个基本単元是储存器和处理器。

* Practically, different phases of an alloy act as poles of tiny electrical cells, as do parts of pure metals.

实际上，合金的不同相起着微型电池两极的作用，正像纯金属的各部分作用一样。 

2. 引导时间状语从句

作为连接词，as可以引导时间状语从句，在句中的位置比较灵活，译为“(当）…… 时”、“随着”等。如：

* As the loop rotates from position A to position B, the conductors are cutting through more and more lines of force until at 90 degrees they are cutting through a maximum number of lines of force.

当线圈从A位向B位旋转时，导线就切割越来越多的磁力线，直到90度时切割磁力线的数目最大为止。

* Human leg veins are repeatedly squeezed by the leg muscles as people walk or run.

当人走路或跑步时，人腿静脉反复受到腿部肌肉挤压。