when基本解釋
副詞當時; 什么時候; （用于時間的表達方式之后）在那時; 其時
連詞如果; 在…時; 既然
代詞什么時候; 那時
名詞時間，時候; 日期; 場合
when的近義詞
when相關例句
副詞
1. When did you last see Margaret?
你上一次見到瑪格麗特是什么時候？
連詞
1.
1. We have only three books when we need five.
雖然我們需要五本書，卻只有三本。
2. We'll start when the team leader comes.
隊長一來，我們就出發。
when情景對話
學校
when是什么意思
B：When is the (assignment/ project/ report) due?
什么時候交（作業/計劃/報告）？
when是什么意思
A：It’s due tomorrow.
明天。
結婚紀念日
A：When is your parents’ wedding anniversary?
你父母的結婚紀念日是在哪天？
when
B：Their anniversary is in August.
他們的結婚紀念日是在八月。
旅游
A：When do we (board/ depart/ arrive)?
我們什么時候（登機（船）？/離開？/到達）？
B：At 6:49pm.
下午6點49分。
when網絡解釋
1. 當......時：-->是I met your sister那當時(when)的特定那一個(指明; 也是關系子句的(形容詞)功能) 夜晚.
when詞典解釋
1. (用于疑問句)什么時候，何時
You use when to ask questions about the time at which things happen.
e.g. When are you going home?...
你什么時候回家？
e.g. When did you get married?...
你什么時候結的婚？
2. (表示兩事同時發生)在…時，當…時
If something happens when something else is happening, the two things are happening at the same time.
e.g. When eating a whole cooked fish, you should never turn it over to get at the flesh on the other side...
吃一整條魚時，切忌把它翻過來去吃另一面的肉。
e.g. Mustard is grown in the field when weeds are there, rather than when the growing crops are there.
芥菜要在地里長雜草而不是長莊稼時種植。
3. (引導從句，表示某事發生于另一活動、事件或情形期間)在…的過程中
You use when to introduce a clause in which you mention something which happens at some point during an activity, event, or situation.
e.g. When I met the Gills, I had been gardening for nearly ten years.
遇到吉爾一家時我已經做了近10年的園藝工作。
4. (引導從句，說明主句動作已經發生或將要發生時的情況)其時
You use when to introduce a clause where you mention the circumstances under which the event in the main clause happened or will happen.
when的近義詞
e.g. When he brought Imelda her drink she gave him a genuine, sweet smile of thanks...
當他把飲料拿給艾梅爾達時，她真誠而甜美地向他微笑以示感謝。
e.g. I'll start to think about it when I have to write my report.
我要寫報告時會對此予以考慮的。
5. (尤用于動詞和形容詞后引導從句，表示某事發生的時間)什么時候,何時
You use when after certain words, especially verbs and adjectives, to introduce a clause where you mention the time at which something happens.
when是什么意思
e.g. I asked him when he'd be back to pick me up...
我問他什么時候回來接我。
e.g. I don't know when the decision was made...
我不知道決定是什么時候作出的。
6. (用于引導從句，限定或指示某事發生的時間)…的時候
You use when to introduce a clause which specifies or refers to the time at which something happens.
e.g. He could remember a time when he had worked like that himself...
他還能記得自己一度工作起來也是那個樣子。
e.g. She remembered clearly that day when she'd gone exploring the rockpools...
她清楚地記得她去巖石區潮水潭探險的那天。
7. (用于引出某個觀點、評論或問題的原因)既然，考慮到
You use when to introduce the reason for an opinion, comment, or question.
e.g. How can I love myself when I look like this?...
我這個樣子，怎么能對自己滿意呢？
e.g. Emerald starlings are fairly small when compared with other such birds.
與同類的其他鳥相比，翠輝椋鳥要小很多。
8. (用于引出使句子的其他部分顯得讓人吃驚或不大可能的事實或評論)雖然，然而,可是
You use when in order to introduce a fact or comment which makes the other part of the sentence rather surprising or unlikely.
e.g. Our mothers sat us down to read and paint, when all we really wanted to do was to make a mess...
我們的母親讓我們坐下來讀書和畫畫，而我們真正想做的卻是打打鬧鬧。
e.g. The temperature sensor is making the computer think the engine is cold when, in fact, it's hot.
溫度傳感器發給計算機的信息為發動機是冷卻的，可實際上它的溫度很高。