[析]在文章中第一次提到某物时用不定冠词，而第二次提到时用定冠词。
[误]Please turn off lights before you leave.
[正]Please turn off the lights before you leave.
[析]虽然是第一次提到某物但说话双方均知其所指，也应用定冠词。
[误]There are nine planets around a sun.
[正]There are nine planets around the sun.
[析]世上独一无二的天体等名词前应加定冠词，如：the earth，the moon，the sun，the sky，the sea.
[误]I live on a second floor of this building.
[正]I live on the second floor of this building.
[析]在序数词，形容词最高级前要用定冠词。如：He is the oldest in the family.
[误]I want to learn the second language this term.
[正]I want to learn a second language this term.
[析]在序数词的含意不是顺序中的第一第二，而其意在于再学一个，再来一个时，应用a，本句的意思应为：这学期我要学一门第二外语。
[误]Mississippi is one of the longest rivers in the world.
[正]The Mississippi is one of the longest rivers in the world.
[析]在河流名称前应加定冠词，如：the Yellow River（黄河）。
[误]Look，there are Alp.
[误]Look，there are the Alp.
[正]Look，there are the Alps.
[析]具体的某一座山不加定冠词，如：Mountain Tai.但在山名称前加定冠词后，其山名要加s，来表示山脉。the Alps即为阿尔卑斯山脉。如：The Alps are in the center of Europe.
[误]Times is one of the oldest newspapers in the world.
[正]The Times is one of the oldest newspapers in the world.
[析]报刊名称前应加定冠词。
[误]Rich are not always happy.
[正]The rich are not always happy.
[析]在形容词前加定冠词表示一类人，而在姓的前面加定冠词，姓后加s表示某一家，如：The turners are going to move to New York.
[误]I like to eat bread for breakfast. Bread sells in this shop is very good.
[正]I like to eat bread for breakfast. The bread sells in this shop is very good.
[析]物质名词特指时也应加定冠词。
[误]The sun rises in east.
[正]The sun rises in the east.
[析]在方向、方位前应用定冠词，如：in the east，in the west，in the north，in the south，in the direction 及in the past，in the future.
[误]Do you know who invented telephone
[正]Do you know who invented the telephone
[析]在特定和专有事物或名称前要加定冠词。
如：the English Channel 英吉利海峡
the Panama Canal 巴拿马运河