定语从句，一个简单句跟在一名词或代词后(先行词)进行修饰限定，就叫做定语从句。下面是小编为大家提供的关于介词和非限制的定语从句，内容如下：
非限定性定语从句：
意义：
非限定性定语从句起补充说明作用，缺少也不会影响全句的理解。在非限制性定语从句的前面往往有逗号隔开，如
(1)The house,which I bought has a lovely garden. 我买的房子带着个漂亮的花园。
(2)This novel, which I have read three times, is very touching. 这本我已经读过三遍的小说很感人。
1.非限定性定语从句可将整个主句作为先行词, 对其进行修饰,这时从句谓语动词要用第三人称单数，例如：
(1)He seems not to have grasped what I meant, which greatly upsets me.他似乎没抓住我的意思，这使我心烦。
(2)Liquid water changes to vapor, which is called evaporation. 液态水变为蒸汽，这就叫做蒸发。
2. 在非限定定语从句中，有时as也可用作关系代词，若as在从句中作主语，其引导的句子可以放在句首，也可以放在句中。例如：
(1)The boy has as much progress as we had expected. 正像我们所预料的那样，这个男孩取得了大的进步。
(2) As everyone knows ,China is a beautiful country with a long history . 每个人都知道，中国是一个有着悠久历史的美丽国家。
3. 在非限定性定语从句中，不能用从句做主语
(1)The boys ，who are playing football ，are from Class One. 在踢足球的男孩们是一班的。
(2)I helped an old man ，who lost his way ，yesterday . 昨天，我帮助了一个迷路的.老人。
介词的正确选择：
1. 根据后面动词和介词的搭配关系选择。如：
①This is not the book of which the teacher spoke in class. (speak of 意为“谈论”，相当于talk about)
②The two things of which they felt proud were Jim’s gold watch and Della’s hair. (be / feel proud of 为固定短语，意为“以……自豪”。)
2. 根据前面的名词的搭配关系选择。如：
①I’ll never forget the day on which I first met him. (表示具体的某一天，介词用on)
②The boy pointed to the direction in which he would run. (“朝……方向”，介词用in)
3. 有时需同时考虑动词和介词的搭配关系及介词和名词的搭配关系。如：
The clever boy made a hole in the wall, through which he could see what was happening inside the house.