Why can’t we use simple sentences for everything?

Simple sentences are great for expressing simple ideas very clearly. Because each sentence offers only one complete thought, however, it can be difficult to use them to show relationships between ideas.

For instance:

This doesn’t do much to tell us about the relationship between things. Why did we buy the sweaters? We liked them, and they were on sale.

Simple sentences also set up a choppy rhythm in our writing. Most of us don’t talk like this. We would say, instead, something like, “We went to the mall, and we stopped at Macy’s. The sweaters were on sale, and we liked them, so we bought them.”

When you combine two or more complete ideas in the same sentence, that’s a compound sentence.

What exactly is a compound sentence?

Let’s review: Simple sentences contain a single, complete thought: a single, independent clause. An independent clause is a clause (group of words) that can stand on its own. It can be a complete sentence.

Compound Sentences combine two complete thoughts – two Independent Clauses – into the same sentence. This is useful when you want to compare things, show a cause and effect relationship, discuss similar thoughts or related topics, or – more basically – if you want to write a bit more like we actually speak.

There are two ways to construct a correct compound sentence.

The first way: Coordinating Conjunctions

The first is the most common. You can connect any two independent clauses (think: simple sentences) by adding a coordinating conjunction and a comma. There are seven coordinating conjunctions:

These seven words (which spell out FANBOYS if listed in this order) can be used to combine two complete sentences. The comma always goes before the conjunction when forming a compound sentence. Here are a few examples:

Notice that every compound sentence has at least two subjects doing at least two actions. The subject might be the same in both parts of the sentence – WE like to bowl, and WE like to skate – but it has to be written out on both sides of the conjunction (and) to make a compound sentence.

Some conjunctions are very common. We use and, but, or, and so every day. And adds information; but contrasts two opposing views; or compares two opposite ideas; and so shows cause and effect.

For, nor, and yet are less common conjunctions:

• Yet suggests a contrast between two items. Think of it as “but also” or “in spite of that.”
• For is a more formal word that, when used to connect sentences, means “because.”
• Nor is used to show two negatives in the same sentence.

A second way! Semicolons

There’s another way to make compound sentences. You can join any two independent clauses by using a semicolon. A semicolon is used to show the closest possible relationship between two ideas.

Semicolons can replace periods. If you have two sentences that are related and want to make them into one, simply remove the period and remove the starting capital letter. That’s the only trick to using a semicolon.

Some books recommend thinking of a semicolon as a replacement for the word “because,” and it can be effective this way:

There is only one space after a semicolon.

So why would I use a semicolon?

The best reason to use a semicolon is that it raises the level of your writing significantly. Used correctly, the semicolon signals to your reader that you’re a college-level writer with mastery of complex grammar.

It’s also a nice tool to have in your toolbox to create variety in your paragraphs. If you’ve used “and” and “but” too many times, mix things up with a semicolon! Just make sure that it has a complete sentence on both sides.

Haven’t I seen you before?

Semicolons are also used in one other way: they can sometimes separate items in complex lists. Don’t be alarmed if you see them doing something like this: We had three criteria in mind when we went house hunting: a big yard, where our kids could play; a big kitchen, where we could make food for all of them; and a very tiny house payment, because we have kids who like to eat.

That’s only for very complicated lists, where using a comma between every item would be confusing. We’ll talk more about this when we discuss comma rules.

Friends of Semicolons

Semicolons often travel with transitional words and phrases. Here’s a list of common transition words:

When these phrases appear as transitions in ANY sentence, they need to be followed by a comma. This is true even after a semicolon.