时间状语从句 要点: 时间状语从句，由如下连词引导：when while as after before as soon as since till /until by the time 在时间状语从句中，要注意时态一致.一般状况下主句是未来时的时候，从句要用一般目前时。 1。when 当。。.的时候mozart started writing music when he was four years old。（当)莫扎特的时候,开始写音乐作品。 2。while 当。.。时 he visited a lot of places while he was traveling.他在旅途中参观了许多地方。 3。as 在。。.的同步；一边.。。一边。.. he smiled as he stood up。他一边站起来一边笑着。 4.after 在。。。之后 he left the classroom after he had finished his homework the other day。 前几天做完作业之后回的家。 5.before 在..。之前 mr. brown had worked in a bank for a year before he came here。 布朗先生来这之前已经在一家银行里工作一年了。 6。as soon as 一。。。就。。。(主将从现) we began to work as soon as we got there.我们一到那就开始工作。 i will write to you as soon as i get home。我一到家就给你写信。 7.since 自。。。以来 到目前 表达自过去的一种起点时间到目前（说话时间)为止的一段持续时间。主句一般用目前完毕时 , 从句用 一般过去时 . mr green has taught in that school since he came to china three years ago。 自格林先生来中国以来，他就在这所学校教书。 （还可以用作介词，本句从句还可以用短语:since three years ago（自三年前以来)表达.) 8 till /until 都可以作连词，连接时间状语，也可以作介词，与其他词构成介词短语，在句中作状语。 they walked till /until it was dark.他们一直走到天黑. xiao ming didn’t leave home till / until his father came back.小明直到他父亲回来才离开家。 9. by the time 到。。。为止 (所在句子的主句应用完毕时） by the time he gets there ， his father has already gone。他到家的时候,他父亲已经走了。 by the time i got to school, the class had already began.我到校时，已经开始上课了. 难点-—as when while 的辨析 as when while 都表达主、从句动作同步发生，三者差异如下: as...
