1、世界上独一无二的事物前面通常要加定冠词：The sun is rising.太阳升起来了。The earth moves round the sun.地球绕着太阳蠕蒜唏怜运行。We have friends all over the world.我们的朋友遍天下。但如果这类独一无二的事物被定语修饰时，则一般不加定冠词：We saw a red sun in the sky.我们看见了天空中的红太阳。There is always a full moon on the night of Mid-Autumn Festival.中秋节之夜总是满月。
2、谈话的双方都知道的人或事物前要加定冠词：They are running to the playground.他们正奔向操场。She is in the garden.她在花园里。Please open the window.请把窗户打开。
3、 前面提到过的人或事物，再提及时要加定冠词：There is a new picture on the wall.The picture is very beautiful.墙上有一张新图画，图画很漂亮。He bought a computer yesterday.The computer in not expensive.他昨天买了一台电脑，电脑不贵。
4、名词被限制性定语修饰时要加定冠词：We like the books he bought for us last year.我们喜欢他去年给我们买的书。Do you know the boy sitting on the ground?你认识坐在地上的那个男孩吗？
5、定冠词与单数名词连用表示一类人或事物：The tiger is a very dangerous animal.老虎是一种非常危险的动物。The recorder is very useful in our English class.录音机在我们的英语课上很有用。
6、定冠词与形容词连用，表示一类人或事物：The young should study hard.年轻人应该努力学习。The students often do some washing for the old.学生们经常为老年人洗衣服。
7、河流、山脉、海洋、群岛等名词前用定冠词：The South China Sea belongs to the People’s Republic of China.南海舛匀砖察属于中华人民共和国。The Changjiang River is the longest river in China.长江是中国最长的河流。但中国的湖泊前有时用定冠词有时可不用：(The) West Lake in Hangzhou is very beautiful.