since when

【问】 I came here in 1950，since when I have been engaged in this work.请解释when及sincewhen从句。

【答】 如同as和which一样，关系副词when(不要与从属连词when相混淆)以及某些介词+when也能引导修饰句子的非限制性定语从句(sentential relative clauses)，即不是修饰名词中心词的定语从句。这时when所代表的常常是前面的句子所提供的时间背景。

1. Two years ago I bought a packet of your razor blades，since when I have used no others.(CGEL)

两年前我买了一包你们的剃须刀片，从那以后我再没用过别的。

2. They settled in Seattle，by when she had obtained a master's degree in economics.(CGEL)

他们在西雅图住了下来，在那之前她已经获得了经济学硕士学位。

3. She joined the editorial staff of a local newspaper，since when she has contributed to vari-ousmonthlies. (CGEL)

她加入了一家地方报纸的编辑组，从那时开始她为各式各样的月刊投稿。