knowledge
1.复数形式knowledges现在很少用，如a man of many small knowledges。但前面可以用a。例如：He has a perfect knowledge of English. 和I have only a slight knowledge of Shanghai.
2.knowledge of English（或Chinese等）不可改作knowledge in English（或Chinese等），也不可改作English（或Chinese等）knowledge。
3.knowledge后面可以接以that引导的从句。例如：He was surprised at the knowledge that his wife was dead.
4.knowledge后面有时接以how，what等词引导的从句。例如：The boy found himself in a boat without the slightest knowledge how he had got there.
5.to my knowledge和within my knowledge意思略有不同。例如：
They have met three times, to my knowledge. （据我所知，他们会见过三次［不是三次以上或以下］。）
They have met three times within my knowledge. （据我已知，他们只会见过三次［不是三次以上］。）
6.关于common knowledge，参见common 2
