[误]This building is an university.
[正]This building is a university.
[析]a用于以辅音音素开始的单词前，而an用于以元音音素开始的单词前，而不是元音字母开头的单词前。university的第一个音素是[j]，所以 用a而不要用an。又如：There is a “n” in the word.是错句，应为：There is an “n”in the word.因字母n的发音的第一个音素是元音。要注意的还有hour因其第一个字母h不发音，所以应该用an hour。例如：
I need an hour to finish the work.
It is a useful dictionary.
It is a European country.
I bought a used car.
[误]I need a umbrella because it looks like raining.
[正]I need an umbrella because it looks like raining.
[析]因umbrella的第一个音素是元音，所以应用an.常用的情况有：an old man, an English teacher, an elephant, an idea, an hour ago, an honest boy…。
[误]“Can you help me” “Sorry, I'm in hurry.”
[正]“Can you help me” “Sorry. I'm in a hurry.”
1.用来表示一类人或事物，如：She is a teacher.
2.指某一类人或事物中的一个，如：An elephant is bigger than a horse.
3.泛指某一人或事物，如：A man is waiting for you at the school gate.
4.相当于“one”的概念，如：I just bought a new dictionary.
如：have a walk/a rest/a look
又如：in a hurry 匆匆忙忙
make a face 作鬼脸
do somebody a favour 帮某人忙
a number of =many
又如：have a good time (玩得好)
have a cold (感冒)
have a headache (头痛)
have a break=have a rest
[误]I bought the dictionary yesterday. A dictionary is very good.
[正]I bought a dictionary yesterday. The dictionary is very good.
[误]Please turn off lights before you leave.
[正]Please turn off the lights before you leave.
[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.
[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.
[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.
[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
如：the English Channel 英吉利海峡
the Panama Canal 巴拿马运河
the Suez Canal 苏伊士运河
[误]Would you please buy some food for the supper
[正]Would you please buy some food for supper
[误]I like to climb the mountain in the autumn.
[正]I like to climb the mountain in autumn.
[析]一年四季前不用定冠词，如：Spring is the best season in a year.
[误]Sometimes my parents come to school to see me.
[正]Sometimes my parents come to the school to see me.
[析]有些名词被用作其本身原来所含目的时不加冠词，如：go to school上学，leave school(辍学)，after school(放学)，但如果当建筑物讲时应加冠词，如例句中其父母来校不是上学，而是看望孩子，则要加定冠词。又如，He was in hospital for two days.(他在医院住院两天了。)而：He went to the hospital to see his mother.他去医院看望他的母亲。
[误]I bought a same dictionary as she bought.
[正]I bought the same dictionary as she bought.
[析]在惯用法the same, the only, the very前的定冠词不可换为不定冠词。
[误]The police caught the thief by his arm.
[正]The police caught the thief by the arm.
[析]这是英文表达法与中文的明显不同之处，也是初学者极易忽视之处。在英语中的某些动词，如：catch(抓)，take(拿)，strike (打),pat(拍)，hit(击)，hold(握)，pull(拉)…动词后应加人，再加介词on, by, in, with…之后要加定冠词，再加人体的某一部位。这时的定冠词千万不要换作his,her,their等词。