A sentence conveys an idea.  Different sentence structures help you convey different types of ideas.

There are four main types of sentence structures.  The simplest is the

• Simple sentence:  A sentence with one independent clause.

Okay, but what is an independent clause?

• Independent clause:  A clause that contains a complete subject and predicate and can stand on its own as a sentence.

A simple sentence is great for conveying a simple idea:  one action, thought, or piece of information.

He went to the store.

She loved writing, reading, and eating.

The house stood high on the hill.

A structure that’s a little more complicated is the

• Compound sentence:  A sentence with two or more independent clauses connected by coordinating conjunctions, semicolons, or dashes.

I love coordinating conjunctions because there are only seven of them in the English language, so they’re easy to memorize.

Coordinating conjunctions:  and, but, or, for, nor, so, yet

A compound sentence works well to convey an idea that has two or more parts of equal importance.

Jane likes hot dogs, and I like hamburgers.

The group laughed, for he wasn’t wearing pants.

She loved to bake cakes, but they tasted awful, so I told her I was gluten intolerant.

I went to the store; she stayed home.

Now we’re up to the intriguing complex sentence.

• Complex sentence:  A sentence that has one independent clause and one or more dependent clauses.  Usually these are connected to the independent clause by subordinating conjunctions or relative pronouns.

Let’s look more closely at the grammatical terms in that definition. 

• Dependent clause (also called a subordinate clause):  A clause that has a noun and verb but can’t stand on its own as a sentence.

Why can’t it stand on its own? In general, a dependent clause does not state a complete idea.  Since a sentence is an idea, an incomplete idea makes for an incomplete sentence.

More specifically, there are several grammatical reasons a clause may be dependent, but the ones we’re focused on here are subordinating conjunctions and relative pronouns.  One of these words or phrases can prevent the clause from being independent.

• Subordinating conjunction: a conjunction that introduces a dependent or subordinate clause.

That’s not very helpful, so let’s look at some examples:

Subordinating conjunctions: after, although, as, as if, as though, because, before, despite, even if, even though, how, if, once, since, so that, than, that, though, unless, until, when, where, whether, while, etc.

These words or phrases introduce a dependent clause and relate it to an independent clause.  They may indicate cause (because, as, since, so that), concession (although, though), condition (if, in case, unless), comparison (than), place (where), or time (once, before, after, while, when).

Let’s look at some examples of dependent clauses that begin with subordinating conjunctions:

Although Jane likes steak.

Because he wasn’t wearing pants.

After I ate breakfast.

I think you can sense that these are all incomplete ideas.  While they each have a subject and verb, they are not independent clauses.  They can’t stand on their own.

Before we turn these into complex sentences, let’s review the other term in the complex sentence definition.

• Relative pronoun:  a word that introduces a dependent clause and connects it to a noun or pronoun in an independent clause.

Relative pronouns are that, which, whichever, whatever, who, whoever, whom, whose, whomever.

Here are some examples of dependent clauses that begin with relative pronouns:

That Jack built.

Who specialized in house calls.

Which had photos of Elijah Wood on it.

As you can see, these are incomplete ideas and incomplete sentences.

So let’s put it all together, adding an independent clause to each dependent clause to create a complex sentence:

Although Jane likes steak, I like hamburgers.

The group laughed because he wasn’t wearing pants.

I washed the dishes after I ate breakfast.

This is the house that Jack built.

My father was a doctor who specialized in house calls.

Jane sat at her desk, which had photos of Elijah Wood on it.

While we’re just dipping our toe into the complex sentence pool, these examples reveal that the complex sentence combines two or more parts more intimately than the compound sentence, because one part is dependent on the other part.

While complex sentences can be compelling and emotional, every complex sentence does not necessarily have those qualities.  These are pretty unexciting complex sentences.  But they give you an idea of how complex sentences are formed.

If you’ve been counting, you know we’ve only covered three types of sentences.  There’s one more type we need to cover before we’re ready for the big excitement.

• Compound-Complex Sentence:  A sentence that has at least two independent clauses and at least one dependent clause.

This type of sentence contains both the qualities of a compound sentence (more than one independent clause) and the qualities of a complex sentence (an independent clause and a dependent clause).  Here are some examples:

The group laughed because he wasn’t wearing pants, so he ran for the house.

I washed the dishes after I ate breakfast, and the sink drain clogged.

This is the house that Jack built, and you can tell he has no experience.

Though Mitchell prefers science fiction, he read The Lord of the Rings, and he enjoyed it very much.

Now that we can recognize the four types, let’s look at how some great authors use these types, and particularly the complex sentence, to create powerful effects.