Are you ready to learn about sentence structure? Great! 

Sentences are nice little packages of words that come together to express complete thoughts. They make it easy to understand ideas and learn information.

We can categorize sentences based on different criteria, and one way to categorize them is based on their structure. When we do this, we find that there are four sentence structures. Let's take a look at each one.

The Four Sentence Structures

A simple sentence contains only one independent clause. An independent clause is a group of words that has both a subject and a verb, and expresses a complete thought.

Here is a sentence diagram of a simple sentence. Note that there is only one horizontal line.

I kicked the ball is an independent clause. It contains a subject (I) and a verb (kicked), and it expresses a complete thought. 

By the way, simple sentences can have compound elements. Jeremy and I kicked the ball. That sentence has a compound subject. Don't confuse these simple sentences with compound sentences.

A compound sentence contains at least two independent clauses. These clauses are joined by a coordinating conjunction or a semicolon. (When you join two independent clauses with only a comma, it's a mistake called a comma splice.)

A coordinating conjunction (for, and, nor, but, or, yet, so) is a word that glues words, phrases, or clauses together.

Here's a sentence diagram of a compound sentence. Note that there are now two horizontal lines, and one is directly below the other.

I kicked the ball is an independent clause.

It hit Tom is also an independent clause. 

And is a coordinating conjunction joining the two independent clauses. 

I kicked the ball, and it hit Tom is a compound sentence. 

Some sentences (Jeremy and I kicked the ball.) might seem like they're compound because they have compound elements, but they're actually simple. Learn more about the differences between simple and compound sentences here.

A complex sentence contains a subordinate clause and an independent clause. A subordinate clause is a group of words that has a subject and a verb but does not express a complete thought.

Here's a sentence diagram of a complex sentence. Note that there are still two horizontal lines, but one of them is below the other and moved to the right.

Tom cried is an independent clause. 

Because the ball hit him is a dependent adverb clause modifying the verb cried. 

Tom cried because the ball hit him is a complex sentence.

Sometimes, it can be hard for people to tell the difference between compound sentences and complex sentences. You can learn more about telling the difference here. 

A compound-complex sentence is just what it seems like it would be. :) It's basically a combination of a compound sentence and a complex sentence. You know what that means, right? It means that these guys contain at least two independent clauses and at least one subordinate clause.

Here's a diagram of a compound-complex sentence. Note that it's a hybrid of a compound sentence and a complex sentence! Two of the horizontal lines are directly above and below each other and the third is hanging out there in the middle.

Tom cried and I apologized immediately are both independent clauses. They're being joined by the conjunction and. 

Because the ball hit him is a dependent adverb clause modifying the verb cried. 

The whole sentence is a compound-complex sentence. 

The great thing about diagramming sentences is that it shows how the parts of a sentence are related. Being able to see a sentence drawn out will help you understand sentence structure. Give it a shot!

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