当先行词是way的时候,且在定语从句中作方式状语时后面的关系代词有三种情况：in which、that（that为关系副词,在从句中不作任何成分）、省略.如：I don't like the way (in which)/(that)/(/) you talk to me.定语从句you talk to me明显缺少方式状语.而way作主语/宾语时,关系词可以选用which/that,如果作宾语也可以省略不用关系词.如：I don't like the way which/that were taught by our teacher.定语从句缺少主语,所以which/that,但不能省略.
as和which在引导非限制性定语从句时,这两个关系代词都指主句所表达的整个意思,且在定语从句中都可以作主语和宾语.但不同之处主要有两点：1.as 引导的定语从句可置于句首,而which不可.2.as代表前面的整个主句并在从句中作主语时,从句中的谓语必须是系动词；若为行为动词,则从句中的关系代词只能用which.如：It rained hard yesterday,which prevented me from going to the park.prevent是行为动词,不能用as.