从一道高考题看when的运用when是中学英语中一个非常活跃的词，其意义丰富，用法灵活，不易被大家掌握。
高考试题经常涉及对when的考查。
请看2004年北京春季高考单项填空第26题：We were swimming in the lake ______ suddenly the storm started.A. whenB. whileC. untilD. before此题考查的就是when的用法，从语境可知，该空表示“正在这时”，答案选A。
下面结合高考试题对when的用法作一归纳，希望对同学们有所帮助。
一、when可以用作从属连词，引导时间状语从句，意为“当……的时候”，从句的谓语动词可以是延续性的（此时相当于while）,也可以是非延续性的。
其引导的时间状语从句通常用现在时表示将来[真题再现]1. —He was nearly drowned once.—When was ____?—______ was in 1998 when he was in middle school.(2002北京春招)A. that; ItB. this; ThisC. this; ItD. that; This2. The reporter said that the UFO_______ east to west when he saw it.(NMET2000)A. was travelingB. traveledC. had been travelingD. was to travel3. —Can I join your club, Dad?—You can when you _____ a bit older.(NMET1994)A. getB. willC. are gettingD. will have got4． When the old man ＿＿＿＿＿＿＿ to walk back to his house, the sun ＿＿＿＿＿＿ itself behind the mountain.（2005湖北卷）Ａ． started；had already hiddenＢ． Had started； had already hiddenＣ． Had started； was hidingＤ． Was starting； hid5． I ＿＿＿＿＿＿＿ have been more than six years old when the accident happened.（2005北京卷）A．shouldn’t B．couldn’tＣ．Mustn’t Ｄ．Needn’tKey AAAAB二、when可以引导时间状语从句，意为“一……就……”，相当于as soon as例I’ll tell her ab out it when she comes back. 她一回来我就把这件事告诉她。
We will stand up when the teacher comes into the classroom. 老师一走进教室我们就起立。
We will start when the team leader comes.队长一来我们就出发。
三、when可以作“如果；要是”解，引导条件状语从句，相当于if。
但when 作“如果；要是”解通常表示对某事是否会发生有把握,if 则表示对某事是否会发生没有把握例 How can you hope for mercy when you show none? 如果你不宽恕别人，你怎么能希望得到别人的宽恕呢？Let me know when you need money. 如果你需要钱就告诉我。
（含有I’m sure you’ll need money之意）Let me know if you need money.(含有perhaps you’ll need money之意)[真题再现]Don’t be afraid of asking for help ______ it is needed.(NMET2003)A. unlessB. sinceC. althoughD. whenｋｅｙ D四、when可以作“既然，考虑到”解，引导原因状语从句，相当于since, now that, as或considering that例I can’t tell you anything when you won’t listen.既然你不想听，我就什么也不告诉你了。
How could you, when you knew that this might damage the apparatus? 既然你知道这样会损坏仪器，你怎么能这样做呢？[真题再现]1． He transplanted the little tree to the garden ＿＿＿＿＿＿＿ it was the best time for it.（2005上海卷）Ａ． where Ｂ． whenＣ． that Ｄ． until2．Why do you want a new job _______ you’ve got such a good one already? (NMET1998)A. thatB. whereC. whichD. whenKey BD五、when可以引导让步状语从句，意为“虽然；然而；可是”，相当于although例She stopped trying, when she might have succeeded next time. 她不再尝试了，虽然下次可能就会成功了。
Professor Li walks to work when he might ride. 李教授虽然有车可坐，但他还是步行去上班。
六、when可以用作等立连词，意为“就在那时/这时”（=at that/this time）,“然后”（=and then）,通常与“be about to do…”、“be doing…”或“be on the point of doing…”连用例We were about to start, when a strong wind came up and it began to rain. 我们正要出发，这时刮起了大风，天开始下起雨来。
We hadn’t been out for long when she felt sick in the stomach. 我们出去时间不长她就感到肚子疼。
I was doing my homework when the telephone rang. 我正在做作业，这时电话铃响了。
[真题再现]1. He was about to tell me the secret _______ someone patted him on the shoulder.(2002上海)A. asB. untilC. whileD. when2. The students _____ busily when Miss Brown went to get a book she ______ in the office. (MET1991)A. had written; leftB. were writing; has leftC. had written; had leftD. were writing; had left3． I was just talking to Margaret when Jackson ＿＿＿＿＿＿＿．（2005湖南卷）A． cut in B． cut downC． cut out D． cut up4． I was on the highway when this car went past followed by a police car. They______at least 150 kilometers an hour.（2005重庆卷）A． should have been doingB． must have been doingC． could have doneD． would have doneKey DDAB七、when可以用作关系副词，引导定语从句。
这时when在定语从句中作时间状语[真题再现]1. The film brought hours back to me ______I was taken good care of in that faraway village.(NMET2001)A. untilB. thatC. whenD. where2. It was an exciting moment for these football fans this year, _____ for the first time in years their team won the World Cup.(2000北京春招)A. thatB. whileC. whichD. when3. I shall never forget those days ______I lived in the countryside with the farmers, ________had a great effect on my life.(1994上海)A. that; whichB. when; whichC. which; thatD. when; whoｋｅｙ CDB八、when可以用作连接副词，引导名词性从句。
when在从句中既起连接作用同时也作状语[真题再现]1. I hate ______ when people talk with their mouths full.(NMET1998)A. itB. thatC. theseD. them2. I remember ______ this used to be a quiet village.(ＮMET1993)A. whenB. howC. whereD. what3. What I asked him is _______the story happened.(ＮMET1990)A. when and whatB. which and whereC. what and whereD. when and where4．As soon as he comes back, I’ll tell him when _______ and see him.（2005北京卷）A． you will comeB． will you comeC． you comeD． do you comeKey AADA九、when可以用于固定句型“hardly…when…”，意为“一……就……”使用该句型时要注意：① hardly 后的谓语动词用过去完成时 ,when后谓语动词要用过去时。