由于定语从句的结构和用法比较复杂，初学者在使用时往往容易犯一些错误，最常见的有如下七种：

一、在定语从句中加了多余的定语。如： 　　
　　1．误：Some of the boys I invited them didn’t come．
　　正：Some of the boys I invited didn’t come．
　　译：我邀请的男孩中有几个没有来。
　　析：应删去them，因为从句的宾语是省略了的whom，who或that。 　?
　　2．误：The book that you need it is in the library．
　　正：The book that you need is in the library．
　　译：你需要的书在图书馆里。
　　析：应删去it，因为从句的宾语是关系代词that。

二、把定语从句谓语动词的单、复数弄错。如： 　?
　　1．误：Anyone who break the law will be punished¹．
　　正：Anyone who breaks the law will be punished．
　　译：任何违犯法律的人将被处罚。
　　析：应改break为breaks，因为who指anyone，是单数。 　?
　　2．误：Those who has finished may go home．
　　正：Those who have finished may go home．
　　译：做完了的人现在可以回家。
　　析：应改has为have，因为who指those，是复数。 　?
　　3．误：He is the only one of the teachers who know French in our school．
　　正：He is the only one of the teachers who knows French in our school．
　　译：他是我们学校中唯一懂法语的人。
　　析：应改know为knows，因为one前有the only之类限定词，定语从句在意义上修饰 的是the only one，是单数，而不是复数名词the teachers。 　?
　　4．误：This is one of the rooms that is free now．
　　正：This is one of the rooms that are free now．
　　译：这是目前空着的房间之一。
　　析：应改is为are，因为one前没有the only之类的限定词，定语从句在意义上修饰的是名词复数the rooms，而不是单数one。

三、误省略了定语从句中作主语的关系代词。如： 　　
　　1．误：Children eat a lot of sugar often have bad teeth．
　　正：Children who that eat a lot of sugar often have bad teeth．
　　译：吃糖多的孩子往往牙齿不好。
　　析：应加上关系代词who或that，因为从句少主语，且主语不能省略。 　?
　　2．误：The key opens the bike is missing²．
　　正：The key that／which opens the bike is missing．
　　译：开这辆自行车的钥匙不见了。
析：应加上关系代词that或which，因为从句少主语，且主语不能省略。

四、定语从句中加了多余的关系副词或介词。如： 　　
　　1．误：The house where he lives in needs repairing．
　　正：The house where he lives needs repairing．
　　或：The house he lives in needs repairing．
　　译：他住的房子需要修理。
　　析：应保留where，删去从句中的in，因为关系副词where在从句中作地点状语，in属多余。或删去关系副词where，因为where在这里的意思是in which，否则介词in就重复了。
    2．误：I still remember the day on when I first came to Beijing．
　　正：I still remember the day when I first came to Beijing．
　　或：I still remember the day on which I first came to Beijing．
　　译：我仍记得我第一次来到北京那天的情景。
　　析：应删去on，因为when在这里的意思是on which，否则介词on就重复了，或把when改为which。 　?

五、在作先行词的时间名词或地点名词后错用了关系代词或关系副词。 　　
　　1．误：I still remember the day when we spent together．
　　正：I still remember the day that／which we spent together．
　　译：我仍记得我们在一起度过的日子。
　　析：应改when为that或which，因为从句中谓语动词spent是及物动词，其后应跟宾语而不是时间状语。 　?
　　2．误：This is the house where we lived in last year．
　　正：This is the house which／that we lived in last year．
　　译：这是我们去年住过的那个房子。
　　析：应改where为which或that，因为从句谓语动词lived后有介词in，其后少介词宾语，而不是地点状语。

六、在先行词reason后错用关系副词why。如： 　　
　　1．误：Have you asked her for the reason why may explain her absence³？
　　正：Have you asked her for the reason that／which may explain her absence？
　　译：你是否向他问过可以解释他缺席的原因？
　　析：应改why为that或which，因为定语从句缺少主语，而不是少原因状语。 　 　　

    2．误：I don’t believe the reason why he has given for his being⁴ late．
　　正：I don’t believe the reason that／which he has given for his being late．
　　译：我不相信他所提供的他迟到的原因。
　　析：应改why为that或which，因为从句谓语动词has given后缺少宾语，而不是缺少原因状语 。

七、误将强调句型当定语从句。如：
　　1．误：It was in the kitchen where the fire broke out．
　　正：It was in the kitchen that the fire broke out．
　　译：大火发生在厨房。
　　析：应将where改that，因为原句还原为The fire broke out in the kitchen后，在语法和句意上均成立，故此题是强调句型，而非定语从句。 　?
　　2．误：Was it because it snowed last night when you didn’t come？
　　正：Was it because it snowed last night that you didn’t come？
　　译：你是否因昨晚下雪而没有来？
析：应将when改为that，因为，原句还原为Because it snowed last night，you didn"t come后，在语法和句意上均成立，故此题是强调句型而非定语从句。