这个是
定语从句中的：介词+
关系代词形式。
关系代词whom, which在定语从句中作介词的宾语时,可以跟介词一起放在主句和从句之间;当
先行词指人时,介词后的关系代词用whom, 其余用which,这时的关系代词不能省略;有时为了使关系代词紧跟它所修饰的先行词,也可以把介词放在从句中有关动词的后面,这时的which可用that替换。当介词放在从句有关动词的后面时,关系代词which, that, whom在口语中和非正式文体中经常省略。如:
This is the room in which he used to live. = This is the room (which / that) he used to live in. 这是他过去居住过的房间。
Who's the man with whom you just shook hands? =Who's the man (that / whom) you just shook hands with? 刚才你与他握手的那个人是谁?
但含有介词的短语动词一般不拆开,介词仍放在动词的后面。如:
This is the book (which / that) I'm looking for. 这就是我在找的那本书。
在这类定语从句中,介词的选择一般根据动词的需要,如上述几例,或者根据先行词来决定。如:
There is a mountain of which the top is always covered with snow. 有一座山顶总是覆盖着雪的山。介词+关系代词"引导的定语从句
关系代词whom, which在定语从句中作介词的宾语时,可以跟介词一起放在主句和从句之间;当先行词指人时,介词后的关系代词用whom, 其余用which,这时的关系代词不能省略;有时为了使关系代词紧跟它所修饰的先行词,也可以把介词放在从句中有关动词的后面,这时的which可用that替换。当介词放在从句有关动词的后面时,关系代词which, that, whom在口语中和非正式文体中经常省略。如:
This is the room in which he used to live. = This is the room (which / that) he used to live in. 这是他过去居住过的房间。
但含有介词的短语动词一般不拆开,介词仍放在动词的后面。如:
This is the book (which / that) I'm looking for. 这就是我在找的那本书。
在这类定语从句中,介词的选择一般根据动词的需要,如上述几例,或者根据先行词来决定。如:
There is a mountain of which the top is always covered with snow. 有一座山顶总是覆盖着雪的山。
How to live longer is a question to which man has tried tofind a good answer for thousands of years.如何才能长寿， 是人类数千年来力图寻求良好答案的问题。（名词answer与to连用）
总结说来，to which的意思要根据前面的先行词结合来翻译，单独的话没有什么意义。
好像有点乱乱的，希望能帮到你，祝你学习进步~~呵呵呵