最近在教学过程中，经常会有学生问道“as”的用法，这个词别看小，但却是各类考试的宠儿，以下是关于"as"的用法解析，包含经典例句、历年真题及易错点提示。
一、连词：表示"当...时"
例句：
"As I was leaving, the phone rang."（我正要离开时，电话响了）
《哈利波特》经典句："As they entered, the walls shook."（他们一进去，墙壁就开始震动）
As the wealth of the country increase , more waste will be produced.
As I look back upon those years , I am struck by Annie’s wisdom.
真题：
2021年高考英语全国卷Ⅲ
"______ the sun rose, the fog gradually disappeared."
A. While
B. As
C. Until
二、连词：表示"因为"（≈because，但语气较弱）
例句：
"As it was raining, we stayed indoors."（因为下雨，我们待在室内）
《傲慢与偏见》："As he had no money, he could not buy her a ring."
As the weather was fine , we decided to walk to the restaurant
Fortunately they had a lot of experience , as the team leader had already worked on more than 70 building in India.
I do not want to disturb Dr Black as she is in a meeting.
真题：
2019年考研英语一完形填空
"______ the experiment failed, they gained valuable data."
三、介词：表示"作为"
例句：
"As a teacher, my duty is to inspire."（作为老师，我的职责是启发学生）
《阿甘正传》经典台词："Life is like a box of chocolates. You never know what you're gonna get."（注：like≈as）
真题：
2020年英语四级翻译题
"______（作为传统艺术），calligraphy reflects Chinese philosophy."
四、比较结构："as...as"（同级比较）
例句：
"She runs as fast as a cheetah."（她跑得像猎豹一样快）
谚语："A man is as old as he feels."（老不老，心说了算）
真题：
2018年高考英语浙江卷
"The new model is ______ the old one, but cheaper."
A. three times as light as
B. as three times light as
五、让步状语从句（倒装结构）
结构：Adj/Adv/N + as + 主语 + 动词
例句：
"Young as he was, he solved the complex problem."（尽管年轻，他解决了难题）
丘吉尔演讲："Difficult as it was, we never lost hope."
真题：
2022年考研英语二翻译题
"______（尽管聪明如他），he failed to see the trap."
六、固定搭配
1. as long as（只要）：
"You can succeed as long as you persist."
2. as soon as（一...就）：
"I'll call you as soon as I arrive."
3. as if/as though（仿佛）：
"He talks as if he knew everything."
真题陷阱：
2016年英语专四语法题
"He acted ______ nothing had happened."
A. even if
B. as though
C. unless