定从句分辨
无逗号即限 eg

o you know the man who spoke just now?(限制性定语从句)
有逗号非限 eg:He has a brother , who works in Guiyang.(非限制性定语从句)
关系所用词 (who;whom;whose;which;that)
随着先行变 (先行:即所被修饰的指人或物是先行词 )
限定先指人
who;whom要当先 eg:We know the students (who/that are very naughty in our school).
that紧跟前
限定先指物
which;that两出现 eg:The jacket (which/that is hanging on the wall) is mine.
缺定用whose eg:This is the girl (whose family is in the northeast.)
缺主用who;that eg: All architect is a person (who/that) designs house and buidings.
Which把物接 eg

lease bring back the dictionary (which/that) I lent you last week.
缺宾找who;whom;that eg:The doctor (who/whom/that)we are talking about can speak French.
who可把whom替
通常可省略 eg:The person (whom/who) I spoke to just now is our teacher
若前有介词
只许which;whom接 eg:The teacher for whom you are waiting is coming.
且不可省略 eg: This is the book to which I referred in my talk.
非限先指人
who;whom两可兼 eg:His father , whom he loved dearly , died last year.
that滚一边 eg:He has a sister , who works in Shanghai is called Liping.
非限先指物
which独得天 eg: I have read the book A Tale of Two Cities , which was written by Charles Dikens.
定从有特殊
自有解决点
先行表时间
用when来当填 eg.He came last night when I was out
先行表地点
where字必须选 eg.The place where I met her was railway station
先行是reason
用why合因原 eg.The reason why he didn’t go to school yesterday is that he was very sick..
先行way置前
用how永不变 eg.This is the way how he worked out the problem.