Sentences - Part 2, Compound Sentences

In part 2 of our sentence series we talk about compound sentences. In this blog we will look at what compound sentences are, and what are the important features we need to consider when writing compound sentences.

What is a compound sentence?

A compound sentence is composed of at least two independent clauses joined by a comma and a co-ordinating conjunction. An independent clause, like a simple sentence, has a subject + verb and carries its own meaning (see the blog post Sentences - Part 1, Simple Sentences for more information).

A compound sentence has the following 'formula':

There are seven co-ordinating conjunctions in English. You can easily remember them by using the acronym FANBOYS. The English co-ordinating conjunctions are:

For has the same meaning as because; use for to introduce a reason or cause.

It is not easy to get there, for you have to hike down a long rail.

And joins sentences that are alike

He dropped the rice ball, and it rolled into a hole in the ground.

Nor means 'not this and not that'; use nor to join two negative clauses. You must use question word order after nor; place the auxiliary verb before the subject.

She didn't talk, nor did she move.

The book isn't very long, nor is it difficult to read.

But joins sentences that are opposite or show contract.

They were happy, but they were poor.

Or joins sentences that give choices or alternatives

He could choose a big box, or he could choose a small one.

Yet has approximately the same meaning as but; that is, it shows contrast or joins opposite. Use yet when the second part (clause) of the sentence says something is unexpected or surprising.

I was scared, yet I was also curious about the old lady.

So joins sentences when the second sentence expresses the result of something described in the first sentence.

The greedy man wanted all the mice's gold, so he pretended to be a cat.

* So (that) can also be used as a subordinator (see Sentences part 3 - Complex sentences) when connecting two clauses for a 'purpose'. In academic writing Therefore would be a more suitable linking word for this reason.

Using a comma with co-ordinating conjunctions

Use a comma before a co-ordinating conjunction in compound sentences only. Do not use a comma to join two words of two phrases in a simple sentence:

Run-ons and Comma Slices

Run-ons and comma slices are similar errors. Both happen when you join sentences incorrectly.

Run-ons happen when you join two simple sentences without a comma and without a connecting word. For example,

Men like to shop quickly women like to browse.

A comma slice error happens when you join two simple sentences with a comma alone. For example,

Men like to shop quickly, women like to browse.

There are three ways to correct run-on and comma slice errors:

* We will look at these in a different blog post

Proofreading techniques: How to find run-ons and comma slices in your writing.

Compound Sentences with Conjunctive Adverbs

A second way to form a compound sentence is as follows:

Independent clause; + conjunctive adverb, + independent clause

Salt water boils at a higher temperature than freshwater; therefore, food cooks faster in salt water.

When writing a compound sentence in this structure, it is important to use the correct punctuation. You should put a semicolon (;) before and a comma (,) after the conjunctive adverb.

Reference: Oshima, A and Hogue A, Introduction to Academic Writing, 3rd Ed., Pearson Longman

In this blog post we reviewed compound sentences. Check out our next blog post in our sentences series, Sentences - Part 3, Complex Sentences