英语的独立主格结构主要表示谓语动词发生的时间、原因、条件或伴随情况等，在许多情况下相当于一个状语从句或并列句。 1. 用作时间状语http://yingyu.chazidian.com The work done (=After the work had been done), we went home. 工作完成后，我们就回家了。 2. 用作条件状语 Weather permitting (=If weather permits), they will go on an outing to the beach tomorrow. 如果天气允许的话，他们将在明天组织一次海滨小游。 3. 用作原因状语 An important lecture to be given tomorrow (=As an important lecture will be given tomorrow), the professor has to stay up late into the night. 因为明天要发表一个重要的演讲，教授不得不熬夜到很晚。 4. 用作伴随状语 He was lying on the grass, his hands crossed under his head (=and his hands were crossed under his head).他躺在草地上，两手交叉枕在脑后。 5. 表示补充说明 A hunter came in, his face red with cold (=and his face was red with cold). 一个猎人走了进来，他的脸冻得通红。 We redoubled our efforts, each man working like two. 我们加倍努力，一个人干两个人的活。 注：独立主格结构表示时间、条件或原因时，相当于一个状语从句，一般放在句首，表示原因时还可放在句末；表伴随状况或补充说明时，相当于一个并列句，通常放于句末。