導語：定語從句有分一般定語從句和特殊定語從句，下面小編講解特殊定語從句，歡迎參考。
■since / until / by when引導的定語從句
定語從句中有一類是since / until / by when引導的定語從句, 這類比較特殊的定語從句，一般都可整合為and連線的並列句。and since / until / by then= since / until / by when
藉助並列句分析解此類定語從句，就會簡單易懂易記。
【典型例題1】
The book was written in 1946, _______ the education system has witnessed great changes.
A. when B. during which
C. since then D. since when
【解析】句意：該書寫於1946年，從那以後教育制度已經歷了 巨大變化。因從句中“has witnessed”是完成時，而只有含 since引導的時間狀語句子才用完成時，故此句可改寫：
The book was written in 1946, and since then the education system has witnessed great changes.
【典型例題2】
The baby is due in May, _______ the new house should be finished.
A. by then B. which
C. by when D. since when
【解析】句意：“那個嬰兒五月將出生，到那時他 / 她家的.新房應該能裝修完畢了。”故此句可改寫：
The baby is due in May, and by then the new house should be finished.
【典型例題3】
I am going back to my hometown this summer, ________I will have enough time to buy a car.
A. by then B. which
C. by when D. since when
【解析】句意：今年夏天我打算回家鄉，到那時我就會有足夠的時間買輛車。從句的時態是將來時，所以排除D，從句中的成分是完整的，排除B，by then不能引導從句，by when在句意和時態上都吻合題意，相當於and by then,故故此句可改寫：
I am going back to my hometown this summer, and by then I will have enough time to buy a car.
【典型例題4】
Tom has been living a comfortable life, _______his parents run away due to heavy debts.
A. until then B. until when
C. since then D. since when
【解析】句意：Tom在父母親的照顧下，過著富裕的生活，直到他父母由於沉重的債務跑掉了。until then 和since then 不能引導從句，since when時態需要用完成時，正確答案是B。
本句可以改寫為：
Tom has been living a comfortable life, and until then his parents run away due to heavy debts.
■which + n. 引導的定語從句
which可以加概括意義的名詞，引導定語從句。
and during / by that time=during / by which time 在那段時間
and in that case = in which case 在那種情況下
and at that point = at which point 在那時
and that language = which language 那種語言
【典型例題1】
He can speak German, ________language I can only follow with difficulty.
A. that B. whose
C. which D. what
【解析】句意：他會說德語，那種語言我要很費力地才能聽懂。A,D不能引導非限制性定語從句，whose和language的關係不是所屬關係，所以答案是which 。此句可改寫：
He can speak German, and I can only follow that language with difficulty.
【典型例題2】
She may be late, ________we ought to wait for her.
A. in which case B. in that case
C. where D. from where
【解析】句意：她可能遲到，那種情況我們該等她。C,D與題意不吻合，in that case不能引導從句，in which case 能引導從句，而且和片語吻合。本句可改寫成：
He may be late and in that case we ought to wait for him
【句子轉換】
1. 他被任命為主席，在那個位置上他度過了餘生。
He was appointed chairman, in which post he spent the rest of his life.
= He was appointed chairman and in that post he spent the rest of his life.
2. 他發了脾氣，在那個時刻我決定回家。
He lost his temper, at which point I decided to go home.
= He lost his temper and at that point I decided to go home.
3. 在家裡，他好像十點半之後才有空，到那時孩子們已上床睡覺了。
At home, he never seems to have time until after 10:30 pm, by which time his children have gone to bed.
= At home, he never seems to have time until after 10:30 pm, and by that time his children have gone to bed.
4. 我們做了三年隔壁鄰居，在此期間我們只見過兩次面。
We were next-door neighbors for three years, during which time we met only twice.
= We were next-door neighbors for three years, and during this / that time we met only twice.
5. 被告知我的工作不能令人滿意，聞訊後我便遞交了辭呈。
I was told my work was unsatisfactory, at which point I submitted my resignation.
= I was told my work was unsatisfactory, and at this / that point I submitted my resignation.
6. 他在學習經濟學，這門知識在當今非常重要。
He is studying economics, which knowledge is pretty important today.
= He is studying economics, and this knowledge is pretty important today.
■after / before which 引導的定語從句
and after / before that = after / before which
【典型例題1】
He was educated at a local grammar school, _______ he went on to Cambridge.
A. from which B. after that
C. after which D. from this
【解析】句意：他在當地一所文法學校上學，之後他便去了劍橋。after that意為“然後，之後”，但不能引導一個定語從句，因此B項也被排除;after which相當於and after that，故此句可改寫為：
He was educated at a local grammar school, and after that he went on to Cambridge.
【典型例題2】
He left his hometown 20 years ago, _______nothing was heard about him.
A. since when B. after that
C. after which D. from this
【解析】句意：20年前他離開家鄉，從那以後再沒有他的訊息。Since when與與過去時態不吻合，需要用完成時;B,D不能接定語從句，所以C正確。本句改寫成：
He left his hometown 20 years ago and after that nothing was heard about him.
句子轉換
我在東關中學工作了九年，之前我在光明中學工作。
I worked in Dongguan Senior Middle School for 9 years, before which I worked in Gunagming Senior Middle School.
= I worked in Dongguan Senior Middle School for 9 years, and before that I worked in Gunagming Senior Middle School.
【小結點撥】
根據上述學習內容，做出如下總結：
1.帶有this, that的短語，引導定語從句時，要將this, that變為 which。
2.帶有then, now的短語，引導定語從句時，要將then, now變為when。
鞏固練習：
believes in public ownership, ______ idea I quite opposed to.
A. this B. that C. which D. what
baby is due in May, _______ the new house should be finished.
A. by then B. by which C. by when D. since when
was a student at this university from 1999 to 2003, _______ he studied very hard and was made Chairman of the Students’ Union.
A. during which time B. for which time
C. during whose time D. by that time
4. The new China was founded in 1949, _______ great changes have taken place.
A. when B. during which C. since then D. since when
