牛津實用英語語法:145 肯定句中 must和 have to的區別
A must表示由說話人加予的義務：
Mother：You must wipe your feet when you come in.
母親：你進屋前必須先蹭腳。
have to則表示外界的義務：
Small boy：I have to wipe my feet every time I come in.
小男孩：我每次進屋前都得先蹭掉鞋上的土。
B 第二人稱的例句
1 說話人的權威
Mother：You must wear a dress tonight.You cant go to the opera in those dreadful jeans.
母親：你今晚必須穿一條禮服裙衣。你可不能穿著那些難看的牛仔服去歌劇院。
Employer：You must use a dictionary.Im tired of correcting your spelling mistakes.
雇主：你必須用字典。我厭煩給你改拼寫錯誤了。
Doctor：You must cut down on your smoking.
醫生：你必須少吸煙。
2 外界的權威
You have to wear uniform on duty， dont you?
你在值班時必須穿制服，是嗎?
You have to train very hard for these big matches，I suppose.
我想，為參加這些大賽你必須刻苦訓練。
Youll have to get up earlier when you start work，wont you?
你開始上班時，就要早起一些了，是嗎?
Youll have to cross the line by the footbridge.
你必須從天橋過馬路。
C 第三人稱的例句
這時must主要用于書面指令或指導：
Railway company：Passengers must cross the line by the footbridge.
鐵路公告：旅客必須由天橋過馬路。
Office manager：Staff must be at their desks by 9∶00。
辦公室經理：工作人員必須在9∶00前到達各自的辦公桌前。
Regulation：A trailer must have two rear lamps.
規章：拖車必須有兩盞后燈。
只不過是講述或評論他人的義務時，則用 have to：
In this office even the senior staff have to be at their desks by 9∶00.
在這個辦公室，就連高級職員也要在9∶00前到達他們各自的辦公桌前。
She has to make her childrens clothes.She cant afford to buy them.
她必須自己給孩子們做衣服穿。她買不起。
Theyll have to send a diver down to examine the hull.
他們必須派潛水員下水去檢查船體。
如果用 must代替上面例子中的 have to，就可能意指說話的人有權下命令這樣做。
但must可用于表示說話人對某種責任、義務是贊成或同意的：
A driver who has knocked someone down must stop.
撞人的司機必須停車。(說話人認為這是司機的責任。)
或表示說話人很強烈地認為應該這樣：
Something must be done to stop these accidents.
必須采取某種措施以防止這些事故。
D 第一人稱的例子
第一人稱為主語時，must和 have to二者之間的差別不那么重要，常常兩種形式都可以用：
Typist：I must/will have to buy a dictionary.
打字員：我必須去買一本字典。
Patient：I must/have to/will have to cut down on my smoking.
患者：我必須減少吸煙。
但在表達習慣時，have to更好：
I have to take two of these pills a day.
我必須每天吃兩片這種藥。
某事對說話人很急迫，或被說話人認為很重要時，則以用must為好：
I must tell you about a dream I had last night.
我必須把我昨晚做的夢告訴你。
Before we do anything I must find my cheque book.
在我們干任何事之前，我必須先找到我的支票簿。
E 其他例句(各種人稱)
You must come and see us some time.
你有空一定來看我們。(這是一種常用的隨便的邀請方式。)
The children have to play in the street till their parents come home.
孩子們不得不一直在馬路上玩到他們的父母回到家里為止。
This sort of thing must stop!
必須制止這種事!(說話人或者有權或者對此事感覺強烈。)
You must write to your uncle and thank him for his nice present.
你必須給你叔叔寫信并感謝他給你的很好的禮物。
If there are no taxis well have to walk.
如果沒有出租車了，我們就不得不步行。
If your father was a poor man youd have to work.
如果你父親是個窮人，你就不得不工作了。
We have to walk our dog twice a day.
我們每天得遛兩次狗。
注意如下常見的例子：
In shop window：Closing down sale!Everything must go!
商店櫥窗里的告白：關門大甩賣!賣完為止!
F 表示過去的義務的肯定句用 had to表示過去的義務時，而且說話人本身的權威和外界的權威無法區分時，只可用一個形式，即had to：
I ran out of money and had to borrow from Tom.
我沒錢花了，不得不向湯姆借錢。
You had to pay duty on that，I suppose?
我想你不得不為那個付了稅吧?
There were no buses so he had to walk.
沒有公共汽車，所以他只好走著去。
A must表示由說話人加予的義務：
Mother：You must wipe your feet when you come in.
母親：你進屋前必須先蹭腳。
have to則表示外界的義務：
Small boy：I have to wipe my feet every time I come in.
小男孩：我每次進屋前都得先蹭掉鞋上的土。
B 第二人稱的例句
1 說話人的權威
Mother：You must wear a dress tonight.You cant go to the opera in those dreadful jeans.
母親：你今晚必須穿一條禮服裙衣。你可不能穿著那些難看的牛仔服去歌劇院。
Employer：You must use a dictionary.Im tired of correcting your spelling mistakes.
雇主：你必須用字典。我厭煩給你改拼寫錯誤了。
Doctor：You must cut down on your smoking.
醫生：你必須少吸煙。
2 外界的權威
You have to wear uniform on duty， dont you?
你在值班時必須穿制服，是嗎?
You have to train very hard for these big matches，I suppose.
我想，為參加這些大賽你必須刻苦訓練。
Youll have to get up earlier when you start work，wont you?
你開始上班時，就要早起一些了，是嗎?
Youll have to cross the line by the footbridge.
你必須從天橋過馬路。
C 第三人稱的例句
這時must主要用于書面指令或指導：
Railway company：Passengers must cross the line by the footbridge.
鐵路公告：旅客必須由天橋過馬路。
Office manager：Staff must be at their desks by 9∶00。
辦公室經理：工作人員必須在9∶00前到達各自的辦公桌前。
Regulation：A trailer must have two rear lamps.
規章：拖車必須有兩盞后燈。
只不過是講述或評論他人的義務時，則用 have to：
In this office even the senior staff have to be at their desks by 9∶00.
在這個辦公室，就連高級職員也要在9∶00前到達他們各自的辦公桌前。
She has to make her childrens clothes.She cant afford to buy them.
她必須自己給孩子們做衣服穿。她買不起。
Theyll have to send a diver down to examine the hull.
他們必須派潛水員下水去檢查船體。
如果用 must代替上面例子中的 have to，就可能意指說話的人有權下命令這樣做。
但must可用于表示說話人對某種責任、義務是贊成或同意的：
A driver who has knocked someone down must stop.
撞人的司機必須停車。(說話人認為這是司機的責任。)
或表示說話人很強烈地認為應該這樣：
Something must be done to stop these accidents.
必須采取某種措施以防止這些事故。
D 第一人稱的例子
第一人稱為主語時，must和 have to二者之間的差別不那么重要，常常兩種形式都可以用：
Typist：I must/will have to buy a dictionary.
打字員：我必須去買一本字典。
Patient：I must/have to/will have to cut down on my smoking.
患者：我必須減少吸煙。
但在表達習慣時，have to更好：
I have to take two of these pills a day.
我必須每天吃兩片這種藥。
某事對說話人很急迫，或被說話人認為很重要時，則以用must為好：
I must tell you about a dream I had last night.
我必須把我昨晚做的夢告訴你。
Before we do anything I must find my cheque book.
在我們干任何事之前，我必須先找到我的支票簿。
E 其他例句(各種人稱)
You must come and see us some time.
你有空一定來看我們。(這是一種常用的隨便的邀請方式。)
The children have to play in the street till their parents come home.
孩子們不得不一直在馬路上玩到他們的父母回到家里為止。
This sort of thing must stop!
必須制止這種事!(說話人或者有權或者對此事感覺強烈。)
You must write to your uncle and thank him for his nice present.
你必須給你叔叔寫信并感謝他給你的很好的禮物。
If there are no taxis well have to walk.
如果沒有出租車了，我們就不得不步行。
If your father was a poor man youd have to work.
如果你父親是個窮人，你就不得不工作了。
We have to walk our dog twice a day.
我們每天得遛兩次狗。
注意如下常見的例子：
In shop window：Closing down sale!Everything must go!
商店櫥窗里的告白：關門大甩賣!賣完為止!
F 表示過去的義務的肯定句用 had to表示過去的義務時，而且說話人本身的權威和外界的權威無法區分時，只可用一個形式，即had to：
I ran out of money and had to borrow from Tom.
我沒錢花了，不得不向湯姆借錢。
You had to pay duty on that，I suppose?
我想你不得不為那個付了稅吧?
There were no buses so he had to walk.
沒有公共汽車，所以他只好走著去。
