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 versus complex sentences and independent versus dependent clauses, and we give plenty of examples of complex sentences.
What is a complex sentence?
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.
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 these.
[Incorrect] When I grow up[/incorrect]
[Correct] When I grow up, I’ll use complete sentences.[/correct]
One of the most common types of complex sentence is 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.
Independent vs. dependent clauses: What’s the difference?
The key to using complex sentences is understanding the difference between independent and dependent clauses. Basically, independent clauses are complete sentences on their own, but dependent clauses are not. However, both kinds of clause contain a subject and a verb, so why is one a complete sentence but not the other?
The short answer is that dependent clauses always start with subordinating conjunctions. In a way, these subordinating conjunctions turn independent clauses into dependent ones.
You’re probably already familiar with some common subordinating conjunctions, such as because, since, if, until, when, even though, in case, while, now that, and certain uses of the prepositions before and after. There are also quite a few less common subordinating conjunctions, so we recommend studying the list included in our subordinating conjunction post until you can recognize them on your own.
With a subordinating conjunction, a clause becomes a description of another clause. In this way, dependent clauses change the meaning of independent clauses. Consider this example of an independent clause:
That sounds scary! Alone, this independent clause means that you must remain at school forever. Now, let’s add a dependent clause to make a complex sentence that clarifies things further:
See how the dependent clause changes the meaning of the main point?
Simple vs. complex sentences
The difference between simple and complex sentences is easier to explain. A simple sentence is any sentence with only one independent clause. Any sentence with more than one clause—including a complex sentence—cannot be a simple sentence.
Interestingly, you can sometimes combine two simple sentences to create one complex sentence, as long as the two sentences are logically related and you add a subordinate conjunction.
How to make a complex sentence
Although conditional sentences get complicated, complex sentences in general have fairly easy grammar rules. As long as you’re using the right subordinate conjunction, you have to worry only about commas in complex sentences.
Whether or not to use a comma depends on which clause comes first:
- If the dependent clause comes first, place a comma between it and the independent clause.
- If the independent clause comes first, no comma is needed.
Here’s a couple of complex sentence examples to illustrate:
More complex sentence examples
Here are some complex sentence examples from famous writers to help you understand how they work. We’ve bolded the subordinate conjunction in each.
Tips for writing complex sentences
Once you get the hang of subordinate conjunctions and dependent clauses, complex sentences don’t seem so complex after all. You can construct them and then improve them using our tips on how to write better sentences.
If you’d still like assistance, you can always download Grammarly to ensure your writing is correct. Grammarly offers features that not only point out mistakes but also suggest better word choices and recommend phrasing to improve clarity. Get Grammarly today and see how your writing improves.