這兩個(gè)詞都是引導(dǎo)時(shí)間狀語從句:
When引導(dǎo)的時(shí)間狀語從句:表主句的動(dòng)作和從句的動(dòng)作同時(shí)發(fā)生,或從句的動(dòng)作發(fā)生在主句之前.如：
1.I was reading a novel when she came in.
她進(jìn)來的時(shí)候,我正讀一本小說.（動(dòng)作同時(shí)發(fā)生）
2.When it rains,I go to school by bus.
下雨的時(shí)候,我坐公花汽車上學(xué)樣.（動(dòng)作同時(shí)發(fā)生,都用現(xiàn)在時(shí).）
3.When he receives the letter,he'll tell us know.(動(dòng)作相繼發(fā)生,主句的動(dòng)作發(fā)生在從句之前,動(dòng)詞用過去完成時(shí),從句用過去式.）
While引導(dǎo)的從句：表示“當(dāng).強(qiáng)調(diào)某一段時(shí)間內(nèi)主句和從句中謂語動(dòng)詞所表示的動(dòng)作同一時(shí)期發(fā)生.如:
1.Never get on or off a bus while it is moving.
汽車在運(yùn)行時(shí),不要上下車.(動(dòng)作同時(shí)發(fā)生,動(dòng)詞都用現(xiàn)在時(shí).)
2.She listened closely while he read.
他讀時(shí),她仔細(xì)聽著.(動(dòng)作同時(shí)發(fā)生,動(dòng)詞都用過去時(shí).)
3.While you are young,you must work hard.
趁你年輕時(shí),要努力工作.(主句的動(dòng)作發(fā)生在從句運(yùn)作發(fā)生的過程中.)
4.I was doing my homework while my brother was playing.
我做功課,而我弟弟在玩游戲.(while含有對(duì)比的意思)