What is a Complex Sentence and How to Write One?

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A complex sentence is a sentence with one independent clause and at least one dependent clause. It works best when you need to provide more information to explain or modify your sentence’s main point. Complex sentences are easy to spot as they often use subordinating conjunctions like because, since, or until to connect clauses.

Why are they called “complex?” Complex sentences are different from simple sentences, but share some similarities with compound sentences. Does that seem complex? Don’t worry; they’re easy to use once you understand how they work, which we explain fully below. We talk about simple vs. complex sentences, and independent vs. dependent clauses, and give plenty of complex-sentence examples.

What is a Complex Sentence?

Complex sentences are one of the four types of sentences based on structure (simple, complex, compound, and compound-complex). Their distinction is that they contain a dependent clause; only complex sentences and complex-compound sentences have them.

Dependent clauses, also known as subordinate clauses, are clauses that cannot stand alone as a complete sentence. Without an independent clause, a dependent clause is just a sentence fragment.

Incorrect: When I grow up

Correct: When I grow up, I’ll use complete sentences.

One of the most common types of complex sentences are conditional sentences, which discuss imaginary situations, often using an if-then structure. In conditional sentences, one clause is true only if both clauses are true.

“If you’re always trying to be normal, you will never know how amazing you can be.” —Maya Angelou

What’s the Purpose of a Complex Sentence?

As opposed to a simple (or single-clause) sentence, complex sentences contain much more information. They’re useful for expressing ideas that need layers of detail for the reader to understand.

While a simple sentence is often enough to give the reader an idea of what you’re talking about, a complex sentence makes that idea even clearer.

For example, you could say ‘The dog barked’. This tells us that the dog barked, but it doesn’t tell us why, where or how this happened.

By writing a complex sentence such as, ‘The dog barked when the squirrel jumped from the tree’, we gain a much clearer understanding of the situation. There’s more information there for us to unpack and understand.

Both simple and complex sentences have their uses, but when we want to convey more ‘complex’ ideas and information to the reader, it’s best to use multi-clause sentences. Otherwise, we’d use lots of simple sentences, which can get boring fast!

Examples of Complex Sentences

In the examples of complex sentences below, the dependent clause comes first. Notice that the dependent clause begins with a subordinating conjunction (words like since, because, while) and that the clauses are separated by a comma:

Because he was late again, he would be docked a day’s pay.
While I am a passionate basketball fan, I prefer football.
Although she was considered smart, she failed all her exams.
Whenever it rains, I like to wear my blue coat.

In the complex sentence examples shown below, the independent clause comes first. Notice that in most examples there is no separation of the clauses by a comma, which is the general rule in complex sentences starting with an independent clause. However, the last example has a comma as it is an example of an extreme contrast. This extreme contrast refers to the clauses expressing ideas that are almost opposite in meaning or that must be heavily emphasized.

Having a party is a bad idea because the neighbors will complain.
I am extremely happy since I retired.
The dog jumped on his lap while he was eating.
Annie was still crying, although she had been happy about the news.

Common Complex Sentence Examples

Complex sentences are a common component of everyday life. Aside from adding flow and variation to conversations, they keep you from sounding robotic and terse.

Because my coffee was too cold, I heated it in the microwave.
Although he was wealthy, he was still unhappy.
She returned the computer after she noticed it was damaged.
Whenever prices go up, customers buy fewer products.
Because I had to catch the train, and as we were short on time, I forgot to pack my toothbrush for our vacation.
As she was bright and ambitious, she became a manager in no time.
Wherever you go, you can always find beauty.
Evergreen trees are a symbol of fertility because they do not die in the winter.
Although it was very long, the movie was still enjoyable.
You should take your car in for a service because it’s starting to make weird noises.
The actor was happy he got a part in a movie even though the part was small.
After the tornado hit, there was very little left standing.
The museum was very interesting, as I expected.
Now that he’s rich and famous, people make allowances for his idiosyncrasies.
Even though he’s thoroughly trained, he still makes a lot of mistakes.
Since winter is coming, I think I’ll knit a warm sweater because I’m always cold.
When she was younger, she believed in fairy tales.
I have to save this coupon in case I come back to the store tomorrow.
Let’s go back to Chez Nous because it’s where we had our first date.
Although my friends begged me, I chose not to go to the reunion.
As genes change over time, evolution progresses.
I really didn’t like the movie even though the acting was good.
When he got a cream pie smashed in his face, everyone laughed.
After being apart for years, he still had feelings for her

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.

How to Create Complex Sentences

Complex sentences include an independent and at least one dependent clause.

Though the dependent clause cannot stand alone as a sentence, it does add to the meaning of the independent clause.

In a complex sentence, the independent and dependent clauses can be put together in a variety of ways. For example:

Dependent followed by independent: In this format, put a comma after the dependent clause.

Because I left work late, I just wanted to get home and relax.

(The dependent clause tells us why Joanne wanted to get home)

Independent followed by dependent: In this format, no comma is needed.

I was feeling extra stressed and tired since it was dark when I got back to my house.

(The dependent clause tells us why Joanne was extra stressed and tired)

Dependent both before and after independent: In this format, a comma is required after the first dependent clause.

While I was careful to observe my surroundings, I almost tripped walking up to my door since I couldn’t see in the darkness.

(The dependent clause establishes a relationship of contrast with the independent clause)

Two dependents followed by an independent clause: In this format, put a comma after each dependent clause.

As soon as I opened the door, and after I had kicked off my shoes, I had a sense that someone was in my house.

(The dependent clauses tell us when Joanne experienced that sense)

Do you see how those ingredients work together to create a complete thought?

While the independent clause doesn’t need the dependent clause to survive as a sentence, the dependent clause adds to the meaning of that dependent clause.

Here are a couple more examples to let you know what ultimately happened at the end of Joanne’s lousy day.

Take notice of their respective structures—the order of the independent (IC) and dependent clauses (DC), and where the commas (if needed) appear.

I continued to walk down the hallway even though I was quite scared. (IC-DC)
After letting out what I thought was an intimidating yell, I was greeted by five of my close friends yelling “Surprise!” (DC, IC)
We all had a good laugh because of my lame attempt to scare away the “bad guys.” (IC-DC)
Since my friends gifted me with a lovely surprise and chocolate cake, even though my birthday started out terribly, it ended in the best way possible. (DC, DC, IC).

3 Tips for Writing Complex Sentences

The basic unit of written English is the complete sentence. A complete, simple sentence will express a single idea, using a subject and a predicate. To connect more than one idea within a single sentence, you can write a complex sentence. Follow these tips when creating a complex sentence:

Aim for clarity. The use of complex sentences allows for greater detail, but complexity isn’t a virtue in its own right. Start with your main idea, expressed in your main clause, and use your subordinate clauses and conjunctions to make it more clear and impactful to your readers.
Beware of the run-on sentence. Complex sentences can easily become too complex, and if you’re not careful, you might find yourself adding clauses to the point of excess, which will confuse your reader and make for inelegant writing.
Add an adverbial clause. An adverb clause can add an element of interest to your sentence by providing additional information about a verb, adjective, or another adverb. For example, “He continued sprinting until he crossed the finish line.” Here, “until he crossed the finish line” is a subordinating clause, specifically an adverb clause

Using Subordinate Clauses in Complex Sentences

As we mentioned earlier, a subordinate clause is another way of terming a dependent clause. Both words, subordinate and dependent, offer clues to help us better understand the function of these clauses in writing. Dependent means contingent on or determined by, whereas subordinate means lower in rank or position. That tells us that – grammatically speaking – subordinate/dependent clauses are not equal to the independent clause in a sentence.

The independent clause and subordinate clause are not equal because the latter cannot form a sentence on its own. The subordinate clause is, as such, dependent on the independent clause to provide the complete meaning.

You cannot create a complex sentence without using a subordinate clause in it. Other types of sentences – compound sentences, simple sentences – can exist without subordinate clauses. When you think about it, the subordinate clause is what makes the sentence ‘complex’. The subordinate clause requires the help of the independent clause for it to make sense. It reaches back or forward across the sentence to contextualize itself, making the sentence more ‘complex’ in the process.

Complex Sentence vs. Compound Sentence: What’s the Difference?

In the English language, compound sentences and complex sentences are two common types of sentence structures, but there are two crucial differences between them:

Clauses: A compound sentence is a sentence comprising two or more independent clauses. A complex sentence is a sentence with one independent clause, also known as the main clause, and one or more dependent clauses, known as subordinate clauses. (There is also a sentence structure called the compound-complex sentence containing two independent clauses and one or more dependent clauses.)
Connectives: The independent clauses in a compound sentence connect with coordinating conjunctions, like “for” and “yet.” A helpful mnemonic device is the acronym FANBOYS, which stands for “for, and, nor, but, or, yet, so.” The independent clauses can also be connected with punctuation, such as a semicolon, or conjunctive adverbs, such as “however” and “nevertheless.” The independent and dependent clauses in a complex sentence join with subordinating conjunctions. Common subordinating conjunctions include “after,” “because,” “than,” “where,” “while,” “if,” and “unless.

Why Complex Sentences Are Important

The main issues related to complex sentences is given below:

Use a comma after a fronted adverbial

Learning how to spot a complex sentence is useful because it helps with punctuating sentences correctly. In particular, it helps with deciding whether to use a comma with the dependent clause.

When your dependent clause is at the front and acts like an adverb – typically stating a time (e.g., When it’s ready), a place (e.g., Where they live), or a condition (e.g., If you were in my shoes) – then it is usual to use a comma after the dependent clause to show where the independent clause starts. When such a clause appears at the back of your sentence, it is usually not offset with a comma.