托福写作中标点符号的用法是许多考生在备考中都容易忽略的一个点，但有的时候标点符号对于句子的影响却非常大，不慎用错一个标点可能导致整句话意义都变了。下面，牛学君来给大家详细解读一下逗号在各种写作句型中的用法。

托福写作中逗号用法一

在并列连词(and， but， for， nor， or， yet )前使用，用来连接句中的各分句。

The principal reason for this is that none of them possesses chlorophyll，and since they cannot synthesize their own carbohydrates， they obtain their supplies either from the break down of dead organic matter or from other living organisms.

托福写作中逗号用法二

用逗号来分隔一系列单词、词组和从句。

Further more the walls of fungal cells are not made of cellulose， as those of plants are， but of another complex sugar like polymer called chitin， thematerial from which the hard outer skeletons of shrimps， spiders， and insects are made.

They are a major cause of structural damage to building timbers， a cause of disease in animals and humans， and one of the greatest causes of agricultural losses.

托福写作中逗号用法三

逗号用来分隔与句子其他部分密切相连的简短插入语或旁白。(较长的，更为突兀的或复杂的插入成分的则用破折号或圆括号。)

Chemical fertilization，for example， helps to produce better crops， but is harmful to the environment.

托福写作中逗号用法四

在并列形容词，即分别修饰同一个名词的形容词之间使用逗号，但也有的形容词之间不加逗号的。

For men， heroism was usually described as bravery and the active，successful over coming of adversity.

托福写作中逗号用法五

用逗号来分隔非限定性修饰语，即该修饰语对于句子的意义并非必不可少。非限定性修饰语与限定性修饰语的区别在于，它即使被省略，也不会改变句子的主要意思。

(1) 同位语。

The canopy， the upper level of the trees in the rain forest， holds aplethora of climbing mammals of moderately large size， which may includemonkeys， cats， civets， and porcupines.

(2) 从句。

The canopy， the upper level of the trees in the rain forest， holds aplethora of climbing mammals of moderately large size， which may includemonkeys， cats， civets， and porcupines.

逗号在托福写作中可以应用于多种句型中，很多同学在考试中不注意标点符号，或者乱点标点，这都是不可取的。希望大家能掌握标点的正确使用方法，在托福写作考试中不要用错。