英语基础写作

1. A comma is used to join coordinate clauses（并列句）. It is put before the conjunction（连词）and, but, or, for, so, nor, or yet.

• We started early in the morning, and before dark we reached the village.
• He wanted to go on, but other people disagreed.
• Hurry up, or we'll miss the train.
• He couldn't do it himself, nor could he find anyone to do it for him.
• Nobody was listening, for everybody was shouting to be heard.
• He tried hard, yet he failed to convince her.

We should remember that coordinate clauseshave to be joined with a comma and a conjunction. One comma alone cannot do the job though it is possible in Chinese. Using a comma to link two clauses is a common mistake which has a name: the comma fault（逗号错误）or the comma splice（逗号拼凑）. But we can use a semicolon（分号）, a dash（破折号）, or a colon（冒号） between two coordinate clauses.

2. A comma is used after an adverbial clause（状语从句）or phrase, including a prepositional and a participial phrase（介词或分词短语）placed before the subject, or inserted in the middle of the sentence:

• When the rain stopped,we continued to work in the fields.
• On hearing about the accident, he went to the site at once.
• Some listeners, bored by the lengthy talk, closed their eyes and dozed off.

If the adverbial element follows the main clause（主句）, no comma is required:

• The students were busy working in the reading-room when the lights went off.

3. Commas are used to separate a series of words or phrases with the same function in the sentence:

• Present at the meeting were Dean Lee, Professor Brown, Associate Professor Major, Miss Lindon, and a few other members of the faculty.
• Every weekend she goes to the nearest supermarket to buy pork, chicken, fish, vegetables, bread and other foods for the next week.
• The children sang, danced, jumped, and chased each other.

The comma before the conjunction and the last item is optional（可选择的）. It can be omitted（省略）if there is no danger of misreading.

4. Nonrestrictive（非限制性的）clauses and phrases are set off（隔离开）by commas:

• At 22 she left the college, where she had spent four fruitful and memorable years. Miss Wang, who has returned from America with a doctor's degree, is going to offer a course in American history.
• Mr. Huang, the new director of the company,will soon announce his plans for reforms.
• The speaker, after glancing at his notes,began to talk about the next point.

Restrictive（限制性）clauses and phrases are not set off by commas:

• The economist who developed this new theory of investment has been awarded a Nobel Prize.
• This is the lab where students listen to tapes and see films.

5. Commas set off parenthetical elements（插入成分）:

• The machines you have supplied us, I'm glad to tell you,work very well.
• Many interesting places in Beijing, such as the Summer Palace and the Temple of Heaven, attract thousands of visitors daily.
• The world's three great religions, Buddhism, Christianity, and Islam,all have believers in China.

6. In dates, a comma is used to separate the day and the year if the order is month - day - year; no comma need be used if the order is day - month - year:

• Hong Kong was restored to China on July 1, 1997.（美式表达）
• She was born on 15 September 1980.（英式表达）

7. With numbers of 1,000 or over, commas or little blank spaces may be used to separate digits（数字）by thousands. From right to left, a comma is placed after every three numerals:

1,253,900 53,807,214 690 843 201 279

Commas in numbers help with the reading: the figure before the last comma is in thousands（千）, and the one before the second comma from the right is in millions（百万）.