定语从句引导词即连词中没有what.有that,who,which,whose,whom,where 等.
1当先行词为人时用who或that .如：He is the man that /who likes playing basketball.
2当先行词为物时用which 或that.如：The book which /that I bought yesteday is very interesting.
总之,what 引导的是宾语从句而不是定语从句.如：I don't know what I should do next.