when詞性有副詞、介詞、連詞和名詞四種。
when，英語。
[英][wen] [美][w?n]
adv.什麽時候; （用於時間的表達方式之後）在那時; 其時; 當時;
conj.在…時; 既然; 如果;
pron.什麽時候; 那時;
n.時間，時候; 日期; 場合。
擴展資料1、[adv.]
(1)[疑問副詞]什麽時候，何時，在什麽情況下；
用於疑問句首，如 When do you begin your classes?
(2)從前，以前；當年: When you were a child, you didn't know what it means.
(3)在……時候：His wife always complains when he smoke.
(4)[關系副詞]彼時，其時:Where when he knows wrong, he doesn't admit.
2、[conj.](常用於連接兩件事)
(1)什麽時候：He told us when to eat.
(2)屆時，在那時：He came at six, when the sun was setting.
(3) 是……的時候了：He came at a time when we needed help.
(4)當……時，在……的時候：When we are at college.
(5)每逢，每當：She smiles when you praise her.
(6)相反，而，卻：To complain of one's lot when one might change it.(本來可以改變自己的命運，卻自怨命苦。)
(7)既然，鑒於：How can he help when they won't let him.
3、[pron.]
什麽時候(常用於定語從句)：It was in the morning, when he died.
4、[n.]
時間：When in doubt, leave out.