每ー个生物体都以某种覆盖物，如壳体、皮肤或膜，使其与外界隔离开来。

* Each type of motor has its particular field of usefulness.

每种型号的发电机都有其特定的适用范围。

* There are three groups of electric motors according to their construction and type of power used: universal, a.c. and d.c.

电动机按照其构造和使用的电源可分为三类：通用电动机，交流电动机和直流电动机。

2. 还原

所谓还原就是将形容词性的物主代词译成这个代词所代替的名词，有时需要増加“该”。如：

* Radio waves are similar to light waves except that their wavelength is much greater.

无线电波与光波相似，但无线电波的波长要长得多。

* The greater the number of the free electrons in a material is, the better its conductivity.

材料的自由电子数量越多，该材料的导电性越好。 

3. 互換

在翻译英语的偏正复合结构的句子时，第三人称单数的形容词性物主代词常与它所代替的名词位置互换。如：

* Its being fusible makes metal into liquid when the temperature is high enough.

由于金属是可熔的，所以当温度相当高吋，它就会成为液体。

* It is possible to differentiate these reactions owing to their difference in intensity.

因为反应的强度不同，所以要把它们区分开来是完全可能的。

4. 转译为反身代词

有时候，形容词性的物主代词可以译成反身代词“自己”。如：

* People would probably have to take so much Valium to jolt their pacemakers that the cure would be worse than the disease.

为了突然改变自己的整律器，人们很可能需要服用大量安定，只是用药的结果比疾病本身更糟。

* Because each gene has its unique sequence of different DNA subunits, the precise sequence can be registered.

因为每个基因的不同的DNA副族都有自己的独特的序列，这一精确的序列可以注册。