1. 分隔定語從句。
先行詞與定語從句之間有時也會插入別的成分，構成先行詞與定語從句的隔離，這種從句叫分隔定語從句。例如：
This is the article written by him that I spoke to you about.
He was the only person in this country that was invited.
①因定語從句過長，為使句子保持平衡，常將定語從句和其所修飾的名詞或代詞分開。
The film brought the hours back to me when I was taken good care of in that faraway village.
②在定語從句中使用“插入語”以增加語言的靈活性。
The pen I thought I had lost is on my desk，right under my nose.
2. as 和 which 引導的定語從句。
① as 有“正如，就像”之意，在非限制性定語從句中充當主語、賓語或表語，從句可位於主句的前面、中間或後面，一般用逗號與主句隔開。
As we had expected，her performance was wonderful.
A panda， as we know，is a lovely animal.
Tom is the tallest in our class，as you know.
但 which 引導的非限制性定語從句一般只能放在主句之後。例如：
The result of the experiment was very good，which we hadn’t expected.
②在主謂賓結構的非限制性定語從句中，which 和 as 作賓語時可互換使用。
He was an Englishman，which / as I knew from his accent.
作主語時通常用 which ，而不用 as .但在“主語 +be+done ”結構中，as 作主語。例如：
He passed the examination，as was known.
③ as 引導非限制性定語從句時，通常用在表示肯定意義的從句中，而不能用在表示否定意義的從句中； which 則不受此限制。例如：
Mummy treats me just as a baby，which （不用 as ） I can’t bear.
She married again，which （不用 as ）was unexpected.
④在賓補結構的非限制性定語從句中，作主語或賓語時，宜用 which ，而不用 as .例如：
He believed in God，which （不用 as ） I find strange.
He changed his mind，which （不用 as ） made me very angry.
⑤定語從句中動詞若為表示知覺的.詞，如 see ，expect ，say ，know 等時，用 as 而不用 which .
As we expected / know， Xiao Ming took the first place in the game.
⑥ as 引導的定語從句與 it 作形式主語的主語從句和以 what 引導的主語從句的區別。試比較：
As is known to everybody，the moon travels round the earth once every month.
It is known to everybody that the moon travels round the earth once every month.
What is known to everybody is that the moon travels round the earth once every month.
3. 定語從句與並列句的識別。
定語從句與主句之間要用“逗號”分隔，並且不能加入 and ， but ， so 等連接詞。並列句一般由 and ， but ， so 等詞連接，或中間用“分號”隔開。例如：
He paid the boy $10 for washing the windows，most of which hadn’t been cleaned for at least a year. （定語從句）
He paid the boy $10 for washing the windows，and most of them hadn’t been cleaned for at least a year. （並列句）
He paid the boy $10 for washing the windows；most of them hadn’t been cleaned for at least a year. （並列句）
Recently I bought an ancient Chinese vase，the price of which was reasonable. （定語從句）
Recently I bought an ancient Chinese vase；the price of it was reasonable. （並列句）
John’s parents kept telling him that he should work hard，but it didn’t help. （並列句）
4. that 引導的定語從句與結果狀語從句的區別。
This is so interesting a book that all of us want to read it. （ so …… that 引導的結果狀語從句）
This is so interesting a book as all of us want to read. （ as 引導的定語從句）
通過以上兩個例句不難看出， so …… that 引導結果狀語從句，而定語從句中先行詞前有 so ， such ， the same 修飾時，常用“ as ”來引導定語從句。
5. 定語從句與同位語從句的區別。
同位語從句是位於名詞 answer ， belief ， doubt ， decision ， explanation ， fact ， hope ， idea ， information ， news ， order ， problem ， promise ， truth 等後的句子，並對這些句詞進行補充説明或解釋；從句一般是一個完整的句子，引導詞 that 只起引導作用，不作句子成分，且 that 不可省略；同位語從句不可用 which 引導。而定語從句通常是一不完整的句子，缺少主語或賓語等。作賓語時， that 可省略。
The fact that she hasn’t known the result of the examination is clear. （同位語從句）
The fact （that / which） she told me yesterday is very important. （定語從句）
「鞏固性練習」
1. _________ is mentioned above， the number of the students in senior high school is increasing.
A. As B. It C. That D. What
2. Now Children like to go to the fast food restaurant， _________ as the name says， eating doesn’t take much time.
A. which B. that C. what D. where
3. Sometimes the earthquake is so violent that it can destroy the whole city， _________ happened in Tang Shan in 1976.
A. as B. that C. where D. like
4. Recently my father bought a Chinese painting， _________ was very reasonable.
A. the price of it B. which price
C. the price of which D. its price
5. We will be shown around the city： schools， museums， and some other places， _________ other visitors seldom go.
A. what B. which C. where D. when
6. We were next-door neighbors for three years， during ________ time we met only twice.
A. which B. this C. in which D. same
7. Living in the central Australia desert has its problems， _________ getting water is not the least.
A. as B. for what C. of which D. for what
8. We should do more such exercises in the future， I think， ________ those we did yesterday.
A. as B. which C. that D. it
9. Gone are the days _________ we spent together in the village.
A. that B. when C. in which D. on which
10. He failed his exam， _________ proves that he wasn’t working hard enough.
A. as B. which C. that D. A and B
11. He must be from Africa， _________ can be seen from his skin.
A. that B. as C. who D. what
「參考答案」
1. A 2. D 3. A 4. C 5. C 6. A
7. C 8. A 9. A 10. D 11. B
