将句式分为以下四类：简单句、复合句、并列句和并列复合句。

Sentences: Simple（简单句）, Compound（并列句）, Complex（复合句），and Compound-Complex Sentence（并列复合句）

A common weakness in writing is the lack of varied sentences. Becoming aware of four general types of sentences--simple, compound, complex, and compound-complex sentence --can help you vary the sentences in your writing.

The most effective writing uses a variety of the sentence types explained below.

首先我们看到的是简单句的成分组成，只要满足主谓结构或是主谓宾结构即可。

1. Simple Sentences（简单句）

A simple sentence has one independent clause （主句）and the most basic elements that make it a sentence: a subject, a verb, and a completed thought.

Examples of simple sentences include the following:

1. Joe waited for the train.
"Joe" = subject, "waited" = verb
 

2. The train was late.
"The train" = subject, "was" = verb
 

3. Mary and Samantha took the bus.
"Mary and Samantha" = compound subject, "took" = verb
 

4. I looked for Mary and Samantha at the bus station.
"I" = subject, "looked" = verb
 

5. Mary and Samantha arrived at the bus station early but waited until noon for the bus.

"Mary and Samantha" = compound subject（并列主语）, "arrived" and "waited" = compound verb （并列谓语）

小贴士：当我们在一篇作文中出现大量的简单句时，我们需要考虑将其转化为并列句或是复合句，其要义就是为简单句增加“an independent clause”（一个独立的从句），当然，有些时候简单句自己也可以充当从句使用。

Tip: If you use many simple sentences in an essay, you should consider revising some of the sentences into compound or complex sentences (explained below).

The use of compound subjects, compound verbs, prepositional phrases (such as "at the bus station"), and other elements help lengthen simple sentences, but simple sentences often are short. The use of too many simple sentences can make writing "choppy" and can prevent the writing from flowing smoothly.  

A simple sentence can also be referred to as an independent clause. It is referred to as "independent" because, while it might be part of a compound or complex sentence, it can also stand by itself as a complete sentence.

接下去我们看到的是并列句，在并列句中最突出的就是句子与句子之间的连词，也就是我们熟知的“FAN BOYS”，切记在作文中写出缺乏连词的“run-on sentence”。

2. Compound Sentences（并列句）

A compound sentence refers to a sentence made up of two or more independent clauses connected to one another with a coordination conjunction. Coordinating conjunctions are easy to remember if you think of the words "FAN BOYS":

• § For

• § And

• § Nor

• § But

• § Or

• § Yet

• § So

Examples of compound sentences include the following:

1. Joe waited for the train, but the train was late.
 

2. I looked for Mary and Samantha at the bus station, but they arrived at the station before noon and left on the bus before I arrived.
 

3. Mary and Samantha arrived at the bus station before noon, and they left on the bus before I arrived.
 

4. Mary and Samantha left on the bus before I arrived, so I did not see them at the bus station.

小贴士：当我们在一篇作文中出现大量的并列句时，我们需要考虑将其转化为复合句，我们需要的不仅是句子形式上的并列，更是语义逻辑上的联系与递进。

Tip: If you rely heavily on compound sentences in an essay, you should consider revising some of them into complex sentences (explained below).

Coordinating conjunctions are useful for connecting sentences, but compound sentences often are overused. While coordinating conjunctions can indicate some type of relationship between the two independent clauses in the sentence, they sometimes do not indicate much of a relationship. The word "and," for example, only adds one independent clause to another, without indicating how the two parts of a sentence are logically related. Too many compound sentences that use "and" can weaken writing.

Clearer and more specific relationships can be established through the use of complex sentences. 

其次，我们来看到复合句的定义，其主句是由一个独立子句或是完整的句子构成，它们缺乏某些要素使得其成为一个复合句。

3. Complex Sentences（复合句：名词从句，定语从句，状语从句）

A complex sentence is made up of an independent clause and one or more dependent clauses（从句） connected to it. A dependent clause is similar to an independent clause, or complete sentence, but it lacks one of the elements that would make it a complete sentence. 

Examples of dependent clauses include the following:

• § because Mary and Samantha arrived at the bus station before noon

• § while he waited at the train station

• § after they left on the bus

Dependent clauses such as those above cannot stand alone as a sentence, but they can be added to an independent clause to form a complex sentence.

在复合句当中，主从连词的运用也显得尤为重要。

Dependent clauses begin with subordinating conjunctions. Below are some of the most common subordinating conjunctions:

• § after

• § although

• § as

• § because

• § before

• § even though

• § if

• § since

• § though

• § unless

• § until

• § when

• § whenever

• § whereas

• § wherever

• § while

A complex sentence joins an independent clause with one or more dependent clauses.

The dependent clauses can go first in the sentence, followed by the independent clause, as in the following:

小贴士：当从属子句位于第一位时，应使用逗号分隔

Tip: When the dependent clause comes first, a comma should be used to separate the two clauses.

1. Because Mary and Samantha arrived at the bus station before noon, I did not see them at the station.

2. While he waited at the train station, Joe realized that the train was late.

3. After they left on the bus, Mary and Samantha realized that Joe was waiting at the train station.

Conversely, the independent clauses can go first in the sentence, followed by the dependent clause, as in the following:

小贴士：当独立子句位于第一位时，不应使用逗号分隔

Tip: When the independent clause comes first, a comma should not be used to separate the two clauses.

1. I did not see them at the station because Mary and Samantha arrived at the bus station before noon.

2. Joe realized that the train was late while he waited at the train station.

3. Mary and Samantha realized that Joe was waiting at the train station after they left on the bus.

Complex sentences are often more effective than compound sentences because a complex sentence indicates clearer and more specific relationships between the main parts of the sentence. The word "before," for instance, tells readers that one thing occurs before another. A word such as "although" conveys a more complex relationship than a word such as "and" conveys.

掉尾句的合理替换复合句，也会为文章增色不少。

The term periodic sentence is used to refer to a complex sentence beginning with a dependent clause and ending with an independent clause, as in "While he waited at the train station, Joe realized that the train was late."

Periodic sentences can be especially effective because the completed thought occurs at the end of it, so the first part of the sentence can build up to the meaning that comes at the end.

Beginning Sentences with "And" or "Because"

Should you begin a sentence with "and" or "but" (or one of the other coordinating conjunctions)?

The short answer is "no." You should avoid beginning a sentence with "and," "or," "but," or the other coordinating conjunctions. These words generally are used to join together parts of a sentence, not to begin a new sentence.

However, such sentences can be used effectively. Because sentences beginning with these words stand out, they are sometimes used for emphasis. If you use sentences beginning with one of the coordinating conjunctions, you should use these sentences sparingly and carefully.

Should you begin a sentence with "because"?

There is nothing wrong with beginning a sentence with "because."

Perhaps some students are told not to begin a sentence with "because" to avoid sentence fragments (something like "Because Mary and Samantha arrived at the bus station before noon" is a sentence fragment), but it is perfectly acceptable to begin a sentence with "because" as long as the sentence is complete (as in "Because Mary and Samantha arrived at the bus station before noon, I did not see them at the station.")

最后，我们谈到并列复合句。其由2个或多个独立子句和1个或多个从句组成，使得句子的结构更加紧密严谨，同时也更为丰富。

4. Compound-Complex Sentence（并列复合句）

A compound-complex sentence contains 3 or more clauses: 2 or more independent and 1 or more dependent clause.

I’m happy, even though I don’t make much money, but my kids are always complaining since we can’t afford to buy the newest toys.

Independent clauses: “I’m happy” and “my kids are always complaining”

Dependent clauses: “even though I don’t make much money” and “since we can’t afford to buy the newest toys”

Linking word: “but”

Robert, a friend I’ve known since high school, doesn’t eat meat – so Barbara made a special vegetarian dish for him.

Independent clauses: “Robert doesn’t eat meat” and “Barbara made a special vegetarian dish for him”

Dependent clause: “a friend I’ve known since high school”

Linking word: “so”

After getting home from work, my brother and I went to the mall last night, while my sister stayed home and studied.

Independent clauses: “My brother and I went to the mall last night” and “my sister stayed home and studied”

Dependent clause: “After getting home from work”

Linking word: “while”

This new laptop computer, which I bought yesterday, has already crashed twice; however, I have no idea why.

Independent clauses: “This new laptop computer has already crashed twice” and “I have no idea why”

Dependent clause: “which I bought yesterday”

Linking word: “however”

 

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