(1)在(当)……的时候(when)： Never get on or off a bus～it is in motion. 汽车开动的时候千万不要上下车。They arrived～we were having dinner. 我们正吃饭的时候，他们到了。He fell asleep～(he was) doing his homework. 他做着做着功课就睡着了。W～(I was) in Russia， I learned Russian. 我是在俄国的时候学的俄语。W～at home，he always watches TV. 在家的时候他总是看电视。W～yet a youth， he gained the first prize in English contest. 他年轻的时候就获得过英语竞赛的第一名。He retained the consciousness of it～asleep. 他在睡梦中对那件事仍念念不忘。〖同〗when;

(2)与……同时(at the same time as)：The children were making a snow man outside～the adults were sitting around the fire. 孩子们在外面堆雪人，大人们在烤火。W～you are sorting your things upstairs，I'll wait downstairs. 你在楼上整理东西时，我在楼下等候。He listened to music～doing his homework/driving. 他一边听音乐，一边做功课/开车。

(3)而(but)： Some people waste food～others are starving. 有的人浪费粮食，而有的人却在挨饿。Chinese like tea～western people prefer coffee. 中国人喜欢喝茶，而西方人则更喜欢喝咖啡。Wood is a natural material，～glass is a manufactured material. 木头是天然材料，而玻璃是人造材料。〖同〗but，though，although;

(4)虽然(although) (fml)： W～we have different tastes in music， we are still good friends. 虽然我们的音乐爱好不同，但我们仍是好朋友。W～the old man felt sympathy for me， he thought he could not give me much help. 虽然这位老人同情我，但他认为他无法给我太多的帮助。〖同〗although，though，but