1 used to show where sb/sth is or where sth happens （用于表示位置或地点）: at the bottom/top of the page 在页的下端／上端He was standing at the door. 他站在门口。Change trains at Chester. 在切斯特转车。We were at home all weekend. 我们整个周末都在家里。Are the children at school? 孩子们都就学吗？‘Where's Peter?’ ‘He's at Sue's.’ (= at Sue's house) “彼得在哪里？”“在休家里。”

2 used to show when sth happens （用于表示时间）: I start work at 9 o'clock. 我9点钟开始工作。at the weekend 在周末at night 在晚上at Easter 在复活节She got married at 18 (= when she was 18). 她18岁结婚。

3 in the direction of sb/sth 面向；朝着；对着: What are you looking at? 你在看什么？He pointed a gun at the policeman. 他用枪对着那名警察。Don't shout at me! 不要向我吆喝！

4 because of sth 因为；由于: I was surprised at her behaviour. 她的行为使我吃惊。We laughed at his jokes. 他的笑话引得我们都笑起来。

5 used to show what sb is doing or what is happening （用于表示某人正在做什么或正在发生的事情）: They were hard at work. 他们在努力工作。The two countries were at war. 两国处于交战状态。

6 used to show the price, rate, speed, etc of sth （用于表示价格、比率、速度等）: We were travelling at about 50 miles per hour. 我们当时以每小时约50英里的速度前进。

7 used with adjectives that show how well sb/sth does sth （用于与形容词连用，表示程度）: She's not very good at French. 她的法语不大好。