1. that 引导定语从句时，如果在从句中充当宾语，that 可以省略
   举例
   • 我喜欢我妈妈给我买的这本书。
   I enjoy the book (that) my mom bought for me.(不建议省略)
   在分析长难句时候，如果见到有两个名词or代词直接放一起，中间没有被连词或者标点符号隔开，通常都是省略that定语从句
   练习
   • The potential evolution of today’s technology, and its social consequences, is dazzlingly complicated, and it’s perhaps best left to science-fiction writers and futurologists to explore the many possibilities we can envisage.
2. 区分限制性定语从句和非限制性定语从句
   举例
   • I love Liu, who is beautiful.
   非限制性，有逗号
   • I love Liu who is beautiful.
   限制性，限制后面条件
   分析长难句时候，非限制性定语从句相当于插入语，可以不看。
   练习
   • Edison, whose inventions have been over 2000, is a famous scientist.
   爱迪生是著名科学家（有2000多项发明）
3. 先行词和引导词之间有介词的情况
   人不用who用whom,物不用 that只能用whitch
   举例
   • He is the man from (whom) we should learn.
   • I will never forget the day on (whitch) I met you.
4. 区别 the same … as；the same … that 引导的定语从句
   举例
   • He is the same man as I love.
   像我爱的人
   • He is the same man that I love.
   是我爱的人
5. as 和 which 引导的非限制性定语从句
   which 引导的非限制性定语从句可修饰前面整个句子，as也可以,但是which只能放主句后面，as可前可后。
   举例
   • He enjoys talking with young ladies, which drives me mad.