定语从句：在复合句中作定语用修饰句子中某一名词或代词的从句叫定语从句.
① 定语从句的位置：放在名词或代词的后面.如：The man who has an umbrella in his hand is my uncle. (手上抓了一把雨伞的人是我的叔叔.)
② 语法术语的改变：被修饰的名词或代词称为先行词；引导定语从句的连接词称为关系词,其中that、which、who称为关系代词,where、when、how称为关系副词.
③ 关系代词或关系副词的作用：
关系代词who、whom 和whose指人,分别在从句中作主语、宾语和定语.which指物that多指物, 有时也指人,它们在从句中可以作主语或宾语.定语从句中关系代词作从句宾语时可以省略.This is the thief (that/who/whom) we have been looking for these days. (这个就是我们近日一直在找的小偷.) / Please find a room which is big enough for all of us to live in. (请找一间足够大能住下我们全体的房间.)
关系副词when或where引导定语从句时,它们在从句中分别作时间状语和地点状语.如：This is the room where they had a quarrel a week ago. (这是一个星期前他们吵架的房间.) / I can never forget the day when I first saw you. (我永远不会忘记第一次见到你的日子.)
④ 限制性定语从句和非限制性定语从句.限制性定语从句在句中不能省略,否则主句意思就不完整.非限制性定语从句和主句之间往往用逗号分开,这种从句是一种附加说明,如果从句子中省去,也不致于影响主句的意思.如：She spent the whole evening talking about her latest book, which none of us had heard of. (她一个晚上都在谈论她最近的书,我们一个人都没有听说过那本书.)
被动语态的构成
被动语态由“助动词be＋及物动词的过去分词”构成.人称、数和时态的变化是通过be的变化表现出来的.现以teach为例说明被动语态在各种时态中的构成.
一般现在时：am／is／are＋taught
一般过去时：was／were＋taught
一般将来时：will／shall be＋taught
现在进行时：am／is／are being＋taught
过去进行时：have／has been＋taught
现在完成时：have／has been＋taught
歌诀是：被动语态be字变,过去分词跟后面.