易错点1、关系代词和关系副词的混用。
例 1. Ill never forget the days when I spent in New York with you. 例 2. Ill never forget the days which I visited New York with you. 析：例 1 中的 when 应改为 which 或 that ；例 2 中的 which 应改为 when .区别关系代词和关系副词的重点是看它们在定语从句中所充当的成分。假如定语从句中缺少主语、宾语，就应考虑用关系代词，如例 1 ；若定语从句中缺少状语，就应考虑用关系副词，如例 2 .
易错点2、固定句式出差错。
例 3. Mary is so lovely a girl as everybody loves her.
例 4. Mary is so lovely a girl that everybody loves.
析：例 3 中的 as 应改为 that ；例 4 中的 that 应改为 as . soas 或 sothat 为固定句式，前者为 as 引导的定语从句， as 在定语从句中作宾语或主语，如例 4 ；后者为 that 引导的结果状语从句，该从句的成分是完整的，不缺少主语或宾语，如例 3 .类似的固定句式还有 the same as， suchas ， asas 等。
易错点3、主谓不同。
例 5. Tom is one of the students who likes swimming.
例 6. Tom is the only one of the students who like swimming. 析：例 5 中的 likes 应改为 like ；例 6 中的 like 应改为 likes .在 one of + 复数名词 + 定语从句结构中，定语从句的先行词是复数名词，故谓语动词要用复数形式，如例 5 ；在 theone of + 复数名词 + 定语从句结构中，先行词是 one ，而不是复数名词，故谓语动词要用单数形式，如例 6 .
易错点4、与强调句型及其他句型的混合。
例 7. Was it in the shop that you bought the recorder that you lost your pen？
例 8. Youd better make a mark at where you have any questions. 析：例 7 中第一个 that 应改为 where ；例 8 中应去掉 at .例 7 为带有定语从句的强调句， you bought the recorder 为定语从句，其引导词应用 where ，后面第二个 that 才是强调句中的 that ，此句可还原为： You lost your pen in the shop where you bought the recorder .例 8 为 where 引导的地址状语从句。
易错点5、对先行词定义不清楚。
例 9. It this library that you visited yesterday？
例 10. Is this the library where you visited yesterday？
析：例 9 中应在 library 后加 the one ；例 10 中的 where 应去掉或改为 that 或 which .在例 9 中， this library 是主语， is 是谓语， that 引导的是定语从句，但没先行词，故应补加先行词；在例 10 中， the library 是先行词，定语从句缺少宾语，故应用 that 或 which 来引导，当然也可以省略。
易错点6、特殊名词作先行词时关系词的选取错误。
例 11. I dont like the way which you speak to her.
例 12. I dont care for pay. I just want to get a job that I can be greatly valued.
析：例 11 中应在 which 前加 in 或将 which 改为 that 或去掉；例 12 中的 that 应改为 where 或 in which .在定语从句中，有的特殊名词作先行词时其关系词的选取有肯定的特殊性，如 way 作先行词时，其引导词可用 that 或 in which 或省略，如例 11 ；与 way 一样的还有 job ， situation ， point ， case 等作先行词时，关系词常用 where 或 in which ，如例 12 .
易错点7、忽视as 和which 引导非限定性定语从句有什么区别 。
例 13. He failed in the exam again， which was expected.
例 14. He failed in the exam again， as was not what he had expected.
析：例 13 中的 which 应改为 as ；例 14 中的 as 应改为 which . as 和 which 虽然都可引导非限制性定语从句，但仍有以下三点不同： as 有正如；就像之意，而 which 没； as 引导的非限制性定语从句可置于句首、句中或句末，而 which 只能置于句末；假如非限制性定语从句是不是定句时，只可以用 which 引导。
易错点8、忽视that 和which 引导限制性定语从句有什么区别。
例 15. This is the most exciting football game which I have ever seen.
例 16. Here are the samples thathad I thought of ityou could have taken with you yesterday.
析：例 15 中的 which 应改为 that ；例 16 中的 that 应改为 which .当先行词被最高级、序数词修饰或先行词本身是不定代词时，只可以用 what 来引导定语从句，如例 15 ；当关系词后面有插入成分时，只可以用 which 来引导定语从句，如例 16 .
易错点9、介词前置出差错。
例 17. The two things with which Marx was not sure were the grammar and some of the idioms.
例 18. Tell him all the things to which he should pay attention. 析：例 17 中的 with 应改为 about 或 of ；例 18 中应把 to 移到 attention 的后面。在定语从句中前置的介词需要和后面的动词或形容词构成固定搭配，如例 17 ；但并非所有些固定搭配中的介词都可前置，如例 18 .
易错点10、which 和whose 的意义不清楚。
例 19. The book which cover is broken is of great help to all of us. 例 20. The book of whose cover is broken is of great help to all of us.
析：例 19 中的 which 应改为 whose ；例 20 中的 whose 应改为 which .在定语从句中，关系代词 which 不可以在定语从句中作定语，但 whose 可作定语， whose + n 等于 the + n + of which 或 of which + the + n 。
