How to Write Complex Sentences: Structure and Rules

Updated January 23, 2019
example of a complex sentence
    example of a complex sentence
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They have “complex” right in their name, but don’t worry – forming complex sentences isn’t as hard as it sounds. Complex sentences vary your sentence style and length, making your writing more interesting for readers. Keep reading to learn the structure and rules for writing complex sentences.

Parts of a Complex Sentence

Complex sentences contain an independent clause and at least one dependent clause (sometimes called a subordinate clause). Unlike compound sentences, which connect two independent clauses, at least half of a complex sentence can’t stand alone as its own complete thought. Take a closer look at each part of a complex sentence.

Independent Clause

The independent clause in a complex sentence contains a subject and a verb. It can stand by itself without additional parts of a sentence. Examples of independent clauses would be:

  • Dinner was very tasty.
  • She returned the earrings.
  • John didn’t buy coffee.

You get the general idea of what is happening in each sentence. However, they aren’t very interesting by themselves. They need a bit more detail to engage the reader.


Dependent Clause

Dependent clauses, also known as subordinate clauses, are incomplete thoughts. They provide more details to a sentence but can’t stand alone as their own sentences. Some examples of dependent clauses include:

  • Because Mateo is a wonderful cook
  • After noticing they were scratched
  • When he realized he had no money

These clauses contain interesting details, but without the context of an independent clause, they don’t make much sense. Complex sentences can have one or more dependent clauses joined by subordinate conjunctions.

Subordinate Conjunctions

Conjunctions are connecting words between two clauses, phrases, or words. Subordinating conjunctions join independent clauses to dependent clauses. They establish relationships between these clauses, such as time, place, purpose, condition, or cause.

Some examples of subordinating conjunctions include:

  • after
  • although
  • as
  • because
  • before
  • even though
  • now that
  • though
  • unless
  • when
  • where
  • while

You’ve probably been taught that you can’t start sentences with these words. That’s true if you’re trying to make a dependent clause work as a complete sentence. However, if you’re writing a complex sentence that ends with an independent clause, you can start sentences with because, unless, while, after, or any other subordinating conjunction.


Examples of Complex Sentences

Now that you know the parts of a complex sentence, you can create your own. If you combine the independent and dependent clauses above, you get complex sentences. Here are examples of these complex sentences (notice subordinate conjunctions in bold):

  • Dinner was very tasty because Mateo is a wonderful cook.
  • She returned the earrings after noticing they were scratched.
  • John didn’t buy coffee when he realized he had no money.

These sentences are already more interesting than their simple forms. But the beauty of complex sentences is your ability to change the form even more. Look what happens when you start the sentence with the dependent clauses:

  • Because Mateo is a wonderful cook, dinner was very tasty.
  • After noticing they were scratched, she returned the earrings.
  • When he realized he had no money, John didn’t buy coffee.

If you’re feeling even more creative, consider adding additional dependent clauses to these sentences:

  • As I expected, dinner was very tasty because Mateo is a wonderful cook.
  • Although she loved them, she returned the earrings because they were scratched.
  • When he realized he had no money, John didn’t buy coffee, which set the tone for the rest of the day.

Even though these dependent clauses make the sentence more interesting, the independent clause in each sentence provides the most important information. Making simple sentences into complex sentences is an effective way to vary your writing style. You can find even more examples of complex sentences to guide you on your sentence structure journey.


Compound vs. Complex Sentences

It’s easy to mix up compound and complex sentences, but the difference is easier than you think. You can tell these sentences apart with these definitions:

  • Complex sentences – Independent clause and dependent clause(s) connected with a subordinating conjunction.
  • Compound sentences – Two independent clauses connected with a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so).

You can also remember the difference by looking at each clause. Does each clause provide equally important information, or is one clause more important than the other? For example:

  • Jessica loves the beach, and she also loves the mountains. (Compound)
  • Jessica loves the beach because the weather is warm. (Complex)

Jessica loves the beach and the mountains equally in the compound sentence. The dependent clause in the complex sentence only explains why she loves the beach; it’s not a new idea. Here’s an example of compound and complex sentences that use the same conjunction in different ways:

  • We decided to buy a car, so we went to the dealership. (Compound)
  • We decided to buy a car so we can travel more easily. (Complex)

This is a tricky one because so is a coordinating conjunction in the first sentence, and a subordinating conjunction in the second sentence. But the first sentence puts the speaker in a new place (the dealership) while the complex sentence simply explains why they want to buy a car.


Compound-Complex Sentences

If you want to get really fancy with your sentences, consider writing compound-complex sentences! These sentences include two independent clauses joined together with a coordinating conjunction as well as a dependent clause joined with a subordinate conjunction. Here’s an example of the sentences above as compound-complex sentences:

  • Jessica loves the beach because the weather is warm, but she also loves the mountains.
  • We wanted to travel more easily, so we went to the dealership because we decided to buy a car.

These sentences can be lyrical and engaging for the reader. But take care to add compound-complex sentences sparingly – they do best when included in a variety of simple, compound, and complex sentences.


Complex Boldness

A complex sentence allows for a thoroughly deep dive. When writing, they allow us to divulge extra details about the characters, setting, and plot. Of course, they also serve their purpose in scholastic essays and a wide range of other writing. For more help on improving your writing, read an informative article about building sentence variety into your paragraphs.