a the在表示一类事物时,有什么区别?

a the在表示一类事物时,有什么区别?
比如下面两个句子 用a the填空
______ tractor is a useful machine for farmers
______ boy is more interested in football than girls

A tractor is a useful machine for farmers
The boy is more interested in football than girls
冠词的用法

二. 教学内容：
（一）什么是冠词?
在汉语中我们说“他住在学院附近”,名词“学院”的前面不需加任何东西.而如果翻译成英语“He lives near the Institute.”Institute的前面必须加一个“帽子样”的东西“the”.汉语对冠词的使用不严格,而英语却十分注意冠词的使用,尤其是单数可数名词前一般必须使用冠词.
除了the之外,名词前面经常加的还有a（an）,这两个词分别称为定冠词和不定冠词,统称冠词.
冠词的作用：一是起发音的辅助作用；二是通过冠词的使用,可以使名词在表达涵义上更加确切,使名词在概念与载体、具体与抽象、微粒与群体、特指与泛指之间呈现出丰富的内涵.一般来说,不定冠词表示泛指,定冠词表示特指.

（二）冠词的用法：
1. 不定冠词的用法
（1）a用在辅音前,an用在元音前
例如：Mr. Brown is an Englishman.
He is a statesman and poet.
（2）表示同种类的全体,这时a可相当于any
例如：A cat is a lovely animal.＝Cats are lovely animal.
（3）a＝one
例如：I have a brother and two sisters.
I want only one apple, not two.
（4）a＝the same
例如：Birds of a feather flock together.
The three boxes are much of a size.
（5）a＝per（每）
例如：They work 12 hours a day.
He often drives at eighty miles an hour.
（6）a＝a certain表示该说话人不认识此人
例如：Do you know a Miss Zhang?
（7）物质名词或抽象名词加a（an）即成普通名词,表示个别化、制成品或种类.
例如：Asparagus（芦笋）is a grass.（a ＝a kind of）
This is a good cloth for spring.
（8）have（take）＋a＋抽象名词,表示抽象名词与动词词形同义
例如：Let’s take a swim. ＝Let’s swim.
Let’s have a chat. ＝Let’s chat.

2. 定冠词用法
（1）由于上下文的关系,某名词所指的东西已非常明显,或已有一定的范围,该名词前加the.
例如：Please pass me the book.
Give me the wallet.
（2）表示该名词为全体总称时
例如：The dog is a faithful animal. ＝Dogs are faithful animal.
（3）前面已提过的名词,再次提到时加the
例如：I have bought an English dictionary and the dictionary is very expensive.
（4）用于补语或从句所修饰的名词之前
例如：This is the desk that was bought by Tom.
He is the sort of person who always makes trouble.
（5）用在宇宙间独一无二的天体名词之前
例如：The sun is in the sky.
（6）用在方位、方向等名词之前
例如：The sun rises in the east and sets in the west.
There is a village on the left side of the hill.
（7）乐器之名词之前要加the
例如：to play the violin（guitar, flute, piano etc.）
（8）在最高级前
例如：She is the tallest girl of her school.
（9）专有名词下列情况可加the:
A. 海河、运河的名称: the Thames
B. 复数形的专有名词：the Bahamas
C. 舰船名称：the Queen Mary
D. 画报、杂志、经典的名称：the Time
E. 公共建筑、机关名称：the White House
F. 国民的总称：the Chinese
G. 用在姓氏名称的复数之前指全家人：the Greens

（三）冠词的省略（零冠词）：
1. 称呼语之前不加冠词
例如：Waiter, bring my bill please.
Jack, give me that book please.

2. 家庭称谓如父母兄弟姐妹之前不加冠词
例如：Mom, will you give me some money?

3. 三餐、餐饮名词之前不加冠词
例如：We ate breakfast at eight o’clock this morning.

4. 运动、游戏、颜色、感官之名词之前不加冠词
例如：He likes skiing better than skating.
I want to play football.

5. 表示官职、身份或亲属关系的名词当补语或同位语时不加冠词
例如：He was elected president.
Mike was elected monitor of his class.

6. school, church, hospital等词指原有的用途时不加冠词,若指建筑物本身或场所时,要加定冠词.
例如：School begins at eight.（school做抽象名词用）

7. 两个相对的名词并用时不加冠词
例如：arm in arm, day by day, hand in hand, face to face, shoulder to shoulder

8. 抽象名词前不加冠词
例如：childhood, neighborhood

（四）定冠词的 “有”与“无”与词义
请看out of question与out of the question,后者比前者只多了一个定冠词“the”,涵义却大不相同,前者为“毫无问题”、“没问题”,后者则表示“根本不可能”、“很有问题”.如果用一句话概括,就能起到过目不忘的神效.
口诀：有the“有问题”,无the“无问题”.

（五）用冠词与不用冠词的区别
at table进餐 at the table在桌子旁
at desk在读书或做作业 at the desk在课桌旁
at school在校上学 at the school在学校
at sea在航海中 at the sea在海边
behind time误期 behind the time落后于时代
by sea乘船 by the sea在海边
go to school（church）上学（做礼拜） go to the school（church）到学校（教堂）去
go to sea出海 go to the sea 去海边
in class在上课/在课内 in the class在班上
in bed 在睡觉/卧床 in the bed在床上
in case of万一,如果 in the case of 就……来说,至于
in front of 在（外部的）前面 in the front of在（内部的）前面
in front of bus在公共汽车的前面（不在车上）
in the front of the bus在公共汽车的前部（在车里）
in future从今往后,将来 in the future未来
in hospital住院 in the hospital在医院里
in office在办公,执政 in the office在办公室里
in place of 代替,而不是 in the place of 在……地方
in prison坐牢 in the prison（因事）在监狱
in red穿着红色的衣服 in the red负债,亏损
in secret秘密,私下 in the secret参与秘密,参与阴谋
of age成年人 of an age同龄人
on earth究竟 on the earth地球上,在世上
on horseback骑着马 on the horseback在马背上
out of office离岗 out of the office离开办公室
out of prison出狱 out of the prison（因事）从监狱出来
out of question毫无疑问 out of the question完全不可能,办不到
come out of hospital（病好）出院 come out of the hospital（因事）从医院出来
come out of prison（刑满）获释 come out of the prison（因事）从监狱出来
go to bed上床睡觉 go to the bed去床边
go to church去做礼拜 go to the church（因事）去教堂
go to court起诉 go to the court（因事）去法院
go to hospital去住院 go to the hospital（因事）去医院
go to prison去坐牢 go to the prison（因事）去监狱
go to school上学 go to the school去学校（办事）
go to college上大学 go to the /a college去一所学院（办事,上班）
go to sea当海员 go to the sea去海滨
keep house管理家务 keep the house守在家里
take place发生 take the place of代替
two of us我们当中的两人 the two of us我们两人（共计两人）

（六）有些介词短语有无冠词,意义区别不大：
at（the）most至多,at（the）first起初,首先,all（the）day整天,catch（a）cold感冒in（the）memory of 纪念,go to（the ）market赶集,去市场,on（a）holiday在假期（the）day before yesterday前天,（the）most of 大多数,with（a）smiling face面带笑容