Chapter 9-2-2: The Compound Sentence

Grammar > Building Sentences > Structure > Compound Sentence

Introduction

A compound sentence consists of two or more independent clauses (or simple sentences) joined by a semicolon (“;”) by co-ordinating conjunctions like "and," "but," and "or" that are preceded by a comma, or with an adverbial conjunction that is preceded by a semicolon and followed by a comma:

Simple

Canada is a rich country.

Simple

Still, it has many poor people.

Compound

Canada is a rich country, but still it has many poor people.


Constructing Compound Sentences

Compound sentences are very natural for English speakers—small children learn to use them early on to connect their ideas and to avoid pausing (and allowing an adult to interrupt):


Today at school Mr. Moore brought in his pet rabbit, and he showed it to the class, and I got to pet it, and Kate held it, and we coloured pictures of it, and it ate part of my carrot at lunch, and ...


Of course, this is an extreme example, but if you overuse compound sentences in written work, your writing might seem immature.

A compound sentence is most effective when you use it to create a sense of balance or contrast between two (or more) equally-important pieces of information.


Common Errors

Comma splices and run-on sentences (also known as fused sentences) are all names given to compound sentences that are not punctuated correctly. The best way to avoid such errors is to either:

  • punctuate compound sentences correctly by using one or the other of the rules further below; or

  • avoid compound sentences and write short sentences that require little or no internal punctuation.

Examples of Incorrect Sentences

If you're curious to see examples of run-on sentences, comma splices, and fused sentences, expand this item.


A run-on or fused sentence happens when writers join two complete sentences without any punctuation mark at all:


Incorrect: It is indeed possible to boost recycling organizations can reward consumers with discounts, deals and social connections.


Correct: It is indeed possible to boost recycling. Organizations can reward consumers with discounts, deals and social connections.


Correct: It is indeed possible to boost recycling; for example, organizations can reward consumers with discounts, deals and social connections.


Correct: It is indeed possible to boost recycling. For example, organizations can reward consumers with discounts, deals and social connections.


Correct: It is indeed possible to boost recycling; organizations can reward consumers with discounts, deals and social connections.


Correct: It is indeed possible to boost recycling, for organizations can reward consumers with discounts, deals and social connections.


Correct: It is indeed possible to boost recycling since organizations can reward consumers with discounts, deals and social connections.


Correct: It is indeed possible to boost recyclingorganizations can reward consumers with discounts, deals and social connections.



A comma splice happens when writers use a comma to join two complete sentences without placing an appropriate connecting word between them or by creating two separate sentences. Grammarians say that the comma just isn't "strong enough" to do the job of making one grammatical sentence out of two sentences in a scenario such as this:


Incorrect: The veiled face of data colonialism has dominated certain countries for some time, a new geopolitical trend aims to free the global south from continued colonialism by information technology.


Correct: The veiled face of data colonialism has dominated certain countries for some time. A new geopolitical trend aims to free the global south from continued colonialism by information technology.


Correct: The veiled face of data colonialism has dominated certain countries for some time, but a new geopolitical trend aims to free the global south from continued colonialism by information technology.


Correct: The veiled face of data colonialism has dominated certain countries for some time. However, a new geopolitical trend aims to free the global south from continued colonialism by information technology.


Correct: The veiled face of data colonialism has dominated certain countries for some time; however, a new geopolitical trend aims to free the global south from continued colonialism by information technology.


Correct: The veiled face of data colonialism has dominated certain countries for some time because no trends existed to free these countries from continued colonialism by information technology.


Correct: The veiled face of data colonialism has dominated certain countries for some time; no trends existed to free these countries from continued colonialism by information technology.


Correct: The veiled face of data colonialism has dominated certain countries for some timeno trends existed to free these countries from continued colonialism by information technology.



How to Create Compound Sentences

There are four ways to create a compound sentence. The form of these sentences is:


① Independent clause; independent clause.

② Independent clause: independent clause.

Independent clause, coordinating conjunction + independent clause.

Independent clause; conjunctive adverb, independent clause.


Here is an explanation for each of these situations:


① The first case involves punctuation. It is possible to join two originally separate sentences (independent clauses) into a compound sentence using a semicolon. Writers do this to show the close relationship between the two clauses.

New York has better clubs; Montréal has better restaurants.
My brother is a journalist; he should know.


The second case also involves punctuation. It is possible to join two originally separate sentences into a compound sentence using a colon. This method shows that the second clause somehow relates to the first one—usually, it's an example or explanation. The relationship cannot be loose. A colon can also be used to place intensify the importance of the second clause.

New York has better clubs: they're the only reason to visit the city.
My brother is in a position to know: he works for The New York Times.
We have already prepared our itinerary: First, we'll get some rest at the hotel. Second, we'll get something to eat. Third, we're going to party like there's no tomorrow.¹


③ Third, people can link two simple sentences together using a coordinating conjunction (for, and, nor, but, or, yet, so). The conjunction is preceded by a comma. Authors use this strategy to show the relationship or contrast between the two clauses.

Montréal has better restaurants, but Toronto has better cinemas.
My brother is a journalist, so he should know.


Finally, a conjunctive adverb (furthermore, moreover, however, nevertheless, indeed, in fact, consequently, therefore, otherwise, meanwhile) that is preceded by a semicolon and followed by a comma can be used.

Toronto has better cinemas; however, New York has better clubs.
My brother is a journalist; therefore, he should know.


¹ Linking two simple sentences together using a coordinating conjunction: You may have observed that the capitalization of the sentence that follows the colon is sometimes different in the examples provided. Some grammarians suggest that it is "optional." In British and Canadian English, the first word of the independent clause following the colon is usually not capitalized. In American English, rules can vary. Note that if the word is a proper noun or an acronym, it is capitalized in all countries. On an entirely different note, if the closely related idea that follows the colon continues into one or more sentences after the compound sentence, it is best to capitalize the first word following the colon. See the "We have already prepared our itinerary" sentence, above.

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