（1）表示主动，正在进行的动作的时候，可以用现在分词来改写。如：
I know the girl who is talking to the teacher.
I know the girl talking to the teacher.
我认识正在和老师说话的那位女孩。
（2）表示被动，已经完成的动作的时候，用过去分词来改写，如：
Shirts which are made of silk are very expensive.
Shirts made of silk are very expensive.
丝织的衬衫很贵。
（3）表示将来的动作，用动词不定式来改写，如：
The problem which is going to be discussed tomorrow is our quarterly meeting.
The problem to be discussed tomorrow is our quarterly meeting.
明天要讨论的问题是我们的季度会议。
扩展资料：
定语从句特定选择关系词
一、只用that不用which
1）当先行词是序数词或被序数词、最高级，关系词用that。
2）当先行词既有人又有物时，用that。
3）当先行词带有the only,the very,the same,the last,the one等词时，用that。
4）当主句中有who或which时，为避免重复用that。
5）当先行词为something，anything，nothing，none，no，little，much，all等不定代词时用that。
二、只用who不用that
1）如果先行词是those,they,all,persons,people,he,anyone,one时用who
2）当先行词指人并含有较长的后置定语从句或在被分割的定语从句中时。
三、只用which不用that
1）当主句先行词后有介词时，用which。例：This is the one of which I'm speaking。
2）非限定性定语从句，用which。
3) 描述句中一般用which。例：Beijing，which was China's capital for more than 800years。
4）those +复数名词之后，多用which .例：Shopkeeper want to keep a number of those goods which sell best。
5）先行词本身是that时，用which。
参考资料：百度百科——定语从句
定语从句改成非谓语的方法如下：
表示主动，正在进行的动作的时候，可以用现在分词来改写。如：
I know the girl who is talking to the teacher.
I know the girl talking to the teacher.
我认识正在和老师说话的那位女孩。
The woman who is waving from the window is my mom.
The woman waving from the window is my mom.
在窗户那边挥手的人是我妈妈。
2. 表示被动，已经完成的动作的时候，用过去分词来改写，如：
Shirts which are made of silk are very expensive.
Shirts made of silk are very expensive.
丝织的衬衫很贵。
I like the building which was designed by Mr. Wu.
I like the building designed by Mr. Wu.
我喜欢这栋被吴先生设计出来的大楼。
3. 表示将来的动作，用动词不定式来改写，如：
The problem which is going to be discussed tomorrow is our quarterly meeting.
The problem to be discussed tomorrow is our quarterly meeting.
明天要讨论的问题是我们的季度会议。
4. 表示正在被进行的动作，用现在分词的被动式来改写。如：
The problem which is being discussed now is our quarterly meeting.
The problem being discussed tomorrow is our quarterly meeting.
现在正在讨论的问题是我们的季度会议。
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