This article was originally published in Arizona State University's Online Study Hub. Content has been redistributed with permission from the university. ASU students can access the original resource here.

Achieving a variety of sentence structures can create interest and complexity in your writing. To understand sentence structure, we must first address the building blocks of a sentence.

What is a Clause?

Clauses are the basic unit of a sentence: they include a subject-verb relationship and can be combined in numerous ways. Sentence structure depends on how clauses are put together, and every sentence contains some form of structure.

To understand clauses, it is important to answer what is considered a sentence. Every sentence has a subject and a verb, meaning that there is a person or object doing an action. Subjects (the noun) typically begin a sentence or clause, while a verb (the action) follows.

Some sample subject-verb connections:

Subjects (nouns/noun phrases): he, it, running, Arizona, Becky, magnificent crocodiles

Verbs: is, goes, facilitates, waddles, devour

• Becky runs.

• Crocodiles devour Becky.

• They waddle to Arizona.

• Traveling tires them.

• The crocodiles of Arizona sleep.

Independent Clause

This is the most important clause type, as independent clauses can generate a complete thought independently without the need for additional clauses. In other words, independent clauses can form standalone sentences.

• Becky dislikes crocodiles.

• Crocodiles like Becky.

Dependent Clause

Dependent clauses have a subject-verb relationship, but they do not form a complete thought. Dependent clauses are dependent on an independent clause, which completes the sentence. These clauses often begin with a dependent marker word or subordinating conjunction like “when,” “if,” or “after”.

Note: having a dependent clause alone creates a sentence fragment, which means an incomplete thought. Not having a subject or a verb also forms a sentence fragment.

• Because Becky didn’t want to be eaten

• When the crocodiles saw her

• If they make it to Arizona

Put together, independent and dependent clauses form several sentence types.

Simple Sentence: Independent Clause

Simple sentences have only one subject-verb relationship, which means a total of one independent clause.

• The crocodiles found Phoenix too hot.

• No one knew where Becky was.

Adding parts of speech that do not have a subject-verb relationship does not change the definition as a simple sentence.

• After running tirelessly away from the swamp, carrying a spear, a bottle of water, and letting out deep sighs, Becky stopped.

• The crocodiles found her trapped in the mud, looking afraid but smelling like a meal.

Complex Sentence: Independent Clause + Dependent Clause

Complex sentences have one independent clause and one or more dependent clauses. 

The independent clause is usually the most important part of the sentence, with dependent clauses providing additional information about what happens in the independent clause. These clauses are typically connected through a subordinating conjunction (examples: which, until, since).

• Becky was lost, which the crocodiles realized.

• After wandering around for several hours, she made a bed of ferns and slept in the swamp until the crocodiles discovered her camp since they were hungry.

Compound Sentence: Independent Clause + Independent Clause

Compound sentences string together two or more independent clauses through coordinating conjunctions (for, and, nor, but, or, yet, so) or punctuation like semicolons, colons, and em dashes.

• Becky ran from the crocodiles, but she was too slow.

• The crocodiles wanted to return home, so they left the desert, and Becky’s ghost was spared from following them any longer.

• The ghost of Becky explored the caverns of Globe, Arizona; she found them beautiful.

Compound-Complex Sentence: Independent Clause + Independent Clause + Dependent Clause

A compound-complex sentence combines two or more independent clauses with one or more dependent clauses. In other words, if you add a dependent clause to a compound sentence, or if you add an independent clause to a complex sentence, it becomes a compound-complex structure.

[Independent clause]; [Independent clause], [Dependent clause].

• Becky’s ghost cheered; the crocodiles had returned home, which meant they would leave her alone.

[Independent clause] [Dependent clause]: [Dependent clause] [Dependent clause], [Independent clause].

• They ran away when the glass shattered: since it was only a matter of time before the crocodiles returned, we had to be ready.

[Dependent clause], [Independent clause], but [Independent clause], for [Independent clause], yet [Independent clause].

• Since my friend needed a break from patching the door, I took over and helped board the windows, but it happened too soon, for the crocodiles were outside, yet we were still unprepared.

As an exercise, go back through this resource, and notice how different sentence structures are put together! Also pay attention to how changing sentence structure affect how information is understood.

Writers each have their own unique approach to putting together parts of a sentence, contributing to their writer's "voice": the next time you read a blog or story, look for patterns in sentence structure from a particular author and how form (blog, novel) and genre (academic, sci-fi) affect the composition of sentences.