What is a Complex Sentence and How to Write One?

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

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:

1. 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.)
2. 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.