一、引導(dǎo)時間狀語從句
1.表示“當(dāng)……的時候”，相當(dāng)于at the moment when。
（1）When we got to the cinema,the film had been on for half an hour.當(dāng)我們到電影院時，電影已經(jīng)放映半小時了。
（2）She was writing a letter when I came in.當(dāng)我進(jìn)來時，她在寫信。
2.表示“一……就……”，相當(dāng)于as soon as。
（1）The students got up when the bell rang.鈴聲一響，學(xué)生們就起床了。
（2）I’ll ring you up when I arrive in Beijing.我一到北京就給你打電話。
3.表示“就在這時；當(dāng)時”，相當(dāng)于just at the moment或just then。
（1）We were about to start out when it began to rain heavily.我們正要啟程，就在這，天下起了大雨。
（2）He had just returned from one business trip when he was asked to make another one.他剛剛出差回來，這時，又叫他再次出差。
4.表示“每當(dāng)；每次”，相當(dāng)于every time或whenever。
（1）She always turns to us for help when she is in trouble.每當(dāng)她遇到困難，她總是向我們求助。
（2）It is freezing cold here when it snows.每當(dāng)這兒下雪，天氣就十分寒冷。
5.表示“當(dāng)……之后”，相當(dāng)于after the time that。
（1）We went home when the film was over.電影結(jié)束以后，我們回家去了。
（2）When she got home，she started to prepare supper.她回到家后，開始準(zhǔn)備晚飯。
二、引導(dǎo)條件狀語從句
when引導(dǎo)條件狀語從句相當(dāng)于if/in case引導(dǎo)的條件狀語從句。
（1）When there is no gravity，our feet can no longer stay on the ground.如果沒有重力，我們的腳就不能再地面上站穩(wěn)。
（2）Turn off the switch when anything goes wrong with the machine.如果機(jī)器發(fā)生故障，就把電閘關(guān)上。
三、引導(dǎo)原因狀語從句
when 引導(dǎo)原因狀語從句時，相當(dāng)于since/now that引導(dǎo)的原因狀語從句。
（1）How can they learn anything when they spend all their spare time watching television?他們把所有的空閑時間都用來看電視了，還能學(xué)到什么東西呢？
（2）Why do you want a new job when you have got such a good one.既然你已經(jīng)有了這么好的一份工作，為什么還要再找新工作呢？
四、引導(dǎo)讓步狀語從句
when引導(dǎo)的讓步狀語從句相當(dāng)于though或although引導(dǎo)的讓步狀語從句。
（1）He usually walks when he might ride.雖然有車可乘，但他通常是步行。
（2）The little girl can tell right from wrong when she is only twelve.這個小女孩雖然只有十二歲卻能分清是非。
五、引導(dǎo)定語從句
when引導(dǎo)定語從句時，有時可用in which或on which來替代。
（1）We’ll put off the picnic until next week,when the weather may be better.我們要把野餐推遲到下周，那時可能天氣好些。
（2）I’ll forget the day when I joined the Party.我將永遠(yuǎn)不會忘記我入黨的那一天。
六、引導(dǎo)名詞性從句
1.引導(dǎo)賓語從句
Please tell us when his father will return from abroad.請告訴我們他父親什么時候從國外回來。
2.引導(dǎo)主語從句
When they will leave for Australia hasn’t been decided.他們什么時候動身去澳大利亞還沒有決定。
3.引導(dǎo)表語從句
The question is when they will get so much money to set up the factory.問題是他們將在什么時候弄到這么多錢來把這個工廠辦起來。