1 表示特指的人或物例：Please hand me the key on the desk. 请把桌上的钥匙递给我。The girl in red is his sister. 穿红色衣服的女孩是他妹妹。 The building over there is the tallest in the town. 那边那幢大楼是这个城里最高的。I like the music of the film. 我喜欢这部电影的音乐。 2 表示双方都知道的或心中明白的人或物例： Shut the door, please. 请关门。Has he returned the book? 那本书他还了吗？ Take the blue one, it is cheaper. 拿那个蓝的，它便宜些 3 第二次提到某人或某物第一次提到时用不定冠词，第二次提到时要用定冠词。例：He saw a house in the distance. Jim's parents lived in the house. 他看见远处有一所房子，吉姆的父母就住在那所房子里。 There was once an old fisherman. The old fisherman had a cat. The cat was white. 4 用在世界上独一无二的名词前这类词有： the sun 太阳, the earth 地球, the moon 月亮, the sky 天空, the world 世界 例：The moon goes round the earth. 月亮绕着地球转。There is not any cloud in the sky. 天空中没有一丝云彩。 It was a fine day in spring. The sun shone brightly. 这是一个晴朗的春日，阳光灿烂。He is the richest man in the world. 他是世界上最富的人。 5 用在表示方向、方位的名词前这类词有： the east 东方，the west 西方，the south 南方， the north 北方，the right 右边，the left 左边 例：The birds are flying to the north. 这些鸟向北方飞去。The moon rises in the east and sets in the west. 月亮从东方升起，在西方落下。 The wind was blowing from the south. She lived to the west of the Summer Palace. 她住在颐和园的西边。 Walk along the road and take the first turning on the right. 沿着这条路往前走，在第一个路口往右拐。He stood at the back of the door. 他站在门背后。 提示方位词成对使用构成平行结构时，不用定冠词。例：The river is two thousand kilometers long from west to east. 这条河自西向2000公里长。 They traveled through the country from south to north. 他们自南向北在这个国家旅行。 6 用在形容词最高级前例：Summer is the hottest season of the year. 夏天是一年中最炎热的季节。 She is the best person for the job. 她是最适合这个工作的人。 Hangzhou is one of the most beautiful cities in the world. 杭州是世界上最美的城市之一。The car is the most expensive of the four. 这部车是四部车中最贵的。 7 用在序数词等前定冠词用在序数词前，也用在表示序列的next, last 等前，还有在表示“同一”或“唯一”等的词前。例：The first man to land on the moon is an American. 第一个登上月球的人是美国人。She was the fifth to climb to the top of the mountain. 她是第五个到达山顶的人。