What is a complex sentence? - Examples and Definitions

Learn how to understand complex sentences

To understand something complicated, you need to break it down into smaller parts. This is also true for complex sentences and since complex sentences are made of clauses, that is what we need to figure out.

There are two main types of clauses in English: dependent and independent. Understanding what they are and the difference between them is mandatory to be able to recognize and dissect complex sentences correctly. Let us begin with independent clauses.

Independent clauses

• An independent clause is a group of words that has one subject and one verb, and expresses a complete thought.

The main concept to understand here is that independent clauses express complete thoughts on their own. They can be full complete sentences themselves and that is why they are called independent. An important aspect of understanding independent clauses is identifying the subject-verb pair correctly. If you need to read up on that, we cover how to isolate them later in this article.

Now, let us take a look at some examples to understand independent clauses better:

“I am self-employed” – this is an independent clause, because we have one subject-verb pair, and this expresses a complete thought.

“Helen Oakheart, mother of two and a terrific friend, has won the seemingly impossible race to the top of the ladder despite having to beat a hundred other contestants” – This is also an independent clause because it has one subject-verb pair and expresses a complete thought. 

Remember that when dealing with sentence structure, it is never about length. Complex sentences can be short, and individual clauses can be long.

“When the bells ring” – this is not an independent clause, because even though we have one subject-verb pair, this phrase does not express a complete thought. It is unclear what happens when the bells ring, and as a reader, you are left expecting more information.

“But he won” – independent clauses may have conjunctions, too. As long as we have one subject-verb pair and a complete thought, the clause is independent.

Dependent clauses

Dependent clauses are very similar to their independent counterparts, with one important difference: they do not express complete thoughts. Instead, they require an independent clause to, sort of, latch on to so together, they can be a complete idea.

• A dependent clause is a group of words that has one subject and one verb, adds extra information to the sentence, and cannot stand on its own

Attentive readers might have noticed that one of the examples from the previous section was a dependent clause. Let us look at it and some more examples to better understand dependent clauses:

“When the bells ring” – this is a dependent clause, because it has one subject-verb pair, and does not express a complete thought.

“Because I know what he said” – we have two dependent clauses in this example. Since there are two subject-verb pairs, you need to separate them and not think of this as a single clause. Both these clauses are dependent because on their own they do not express complete thoughts.

“There is nothing else” - this is not a dependent clause, because this sentence expresses a complete thought.

A word on conjunctions

Determining clause type by asking yourself if the clause expresses a complete thought or not is a valid strategy. However, there is another technique you can use to assist this process in case you are not sure what type of clause you are looking at. You can look at the conjunction because dependent and independent clauses use different conjunctions that do not cross over. 

Independent clauses do not always have conjunctions, in fact, it is very common for them to have no conjunction whatsoever. When they do, the list of possible conjunctions is relatively short, and there is an easy acronym to remember them all. Meet the FANBOYS:

For – He went to Spain for he needed a vacation.

And – I work in a vet clinic and I have 2 pets myself.

Nor – This wasn’t helpful nor was it entertaining.

‍But – She doesn’t know chemistry but she knows her biology.

Or – We can have tea or we can have coffee.

Yet – He knew the risks yet he decided to go for it.

So – I needed help so I called my friend.

So, if you see one of these conjunctions in front of a clause, it means the clause is independent. Remember that independent clauses can absolutely exist without conjunctions. In the examples above, the clauses preceding the clauses with conjunctions are also independent.

Dependent clauses, on the other hand, always have a conjunction or a relative pronoun in front of them, because we need it to establish that this clause provides extra information and is not a separate idea. The details of different types of conjunctions and pronouns used with dependent clauses are not important for the task of identifying a dependent clause so we are going to skip that for now. Simply remember that any sort of connective word used with a clause other than FANBOYS means that this clause is dependent.

There is one tricky connective used with dependent clauses and it is the word “that”. The tricky part is that it can often be omitted so if you are not careful, you can mistake a dependent clause for an independent one. Moreover, many dependent clauses with “that” look like independent clauses without it. To avoid this, check that the word “that” can be placed in the clause you are working with. This would mean that the connective was omitted, and the clause is dependent. 

“I know he works there” – if we look at “he works there” separately, it looks like an independent clause. However, if we look at the entire sentence, we can see that a connective was omitted. “I know that he works there”. In this example, “he works there” is a dependent clause with the omitted connective “that”.

Now that we know the basics of clauses, it’s time to put everything together and figure out what complex sentences are.

Complex sentence definition

So what is a complex sentence? Let’s look at the definition first:

• A complex sentence is a sentence that consists of one independent clause and at least one dependent clause.

The important thing to understand here is that the defining characteristic of complex sentence structure is the subordinate connection between clauses. Clauses can be combined in many different ways in English, but only those sentences that combine a dependent with an independent clause are complex. Let us look at some complex sentence examples:

“I know where he works” – “I know” is an independent clause, and “where he works” is a dependent clause, making this sentence complex.

“Even though the leaves have already started falling, many trees were still green” – This is a complex sentence with the dependent clause in front of the independent. The standard order is independent first, dependent second, but this order is not set in stone and you can move them around as much as you want. Just remember to put a comma if you are putting the dependent clause first!

Complex vs compound sentence

Some confusion may arise here because complex and compound sentences look very similar at first glance. However, if you understand the two types of clauses, the difference between these sentence types is as apparent as night and day. Let’s look at the definition of compound sentences and some examples:

• A compound sentence is a sentence that consists of two or more independent clauses

So the difference between complex and compound sentences is the difference between independent and dependent clauses. Complex sentences join dependent clauses. However dependent clauses cannot exist on their own, so they need just one independent clause to connect to. Compound sentences, on the other hand, connect multiple independent clauses.

“I don’t eat most seafood but I like shrimp” – This is a compound sentence with two independent clauses: “I don’t eat most seafood” and “but I like shrimp”.

“I bought some groceries and went home” – This is a compound sentence because it joins two independent clauses. In the second clause “went home”, the subject “I” is omitted to avoid repetition but it is still implied.

“You know what I’m talking about” – this is not a compound sentence, it is complex instead because it joins a dependent clause “what I’m talking about” to the independent “You know”.

It is worth noting that clauses can be combined in any way possible. A sentence can have any number of dependent and independent clauses in any grammatically correct order imaginable. Because of that, an interesting situation may happen. Let us look at the sentence below:

“He walked into the room, looked around, and said that everyone needed to leave”

Let’s identify the clauses here first:

‍“He walked into the room” – an independent clause.

“Looked around” – an independent clause with the subject “he” omitted.

“And said” – an independent clause with, once again, the subject “he” omitted.

“That everyone needed to leave” – a dependent clause.

This particular example does not fit the compound sentence definition because it has a dependent clause, nor does it for the complex sentence definition because it has three independent clauses. What is it then?

Such sentences are classified as compound-complex because they combine the compound sentence coordinate connection and the complex sentence subordinate connection. The compound-complex sentences are very common both in writing and in speech and it is very important to be able to recognize them to avoid confusion.

How to write a complex sentence

When it comes to composing a complex sentence, it helps a lot not to simply know the definitions and be able to identify sentence type correctly, but really understand the purpose of dependent clauses. Dependent clauses exist to provide additional information to an independent clause, and they can do it in a number of ways:

• When, how, or why
• Extra information about a thing or a person
• Substitute for a thing or a person
• Conditions

So, to compose a complex sentence, you should start with an independent clause, and then add extra information to it in one of these ways. Let’s do this step by step:

Compose an independent clause

Any simple sentence will do, just make sure it expresses a complete thought and has one subject-verb pair.

• George bought a new TV.

Add a dependent clause

Dependent clauses function similarly to certain parts of sentence like adverbs and adjectives, so you just need to make sure that it’s not simply a word or a phrase, but a full clause with its own subject-verb pair.

1. When, how, and why.
   • ‍When? – George bought a new TV when the store opened.
   • How? – George bought a new TV like it wasn’t a major purchase.
   • Why? – George bought a new TV because he got tired of his old one.

2. Extra information about a thing or a person
   • George, who lives next door, bought a new TV.
   • George bought a new TV that has an OLED matrix.

3. Substitute for a thing or a person
   • George bought what I call a classic entertainment unit.

4. Conditions‍

A conditional sentence is always a complex sentence because it always consists of one dependent and independent clause. They are easier to compose from the ground up:

• I will help you if you help me.
• I would be able to see it unless the person was blocking the view.
• If you had a superpower, what would you do?
• I wouldn’t do that if I were you.
• If you do nothing, nothing happens.

Just make sure you don’t add extra clauses to your conditional sentences and leave them at one conditional clause and one result clause. Otherwise, you might make it a compound-complex sentence accidentally like so:

“If you take the bags, I will take the boxes and bring them upstairs” – this is a compound-complex sentence because we have two independent clauses here: “I will take the boxes” and “(I will) bring them upstairs”.

Key takeaways

Identifying and composing complex sentences correctly is all about the clauses and their types. Getting comfortable with them and learning to recognize them is what will let you be confident with complex sentences. It is also important to understand the meaning and the purpose of dependent clauses as this will make it easier to memorize definitions and compose your own complex sentences.

FAQ

What are some common conjunctions for complex sentences?

Some common conjunctions that introduce dependent clauses include: Cause/reason: because, as, since; Time: when, before, after, while; Condition: if, unless; Purpose: so that, in order that; Extra information about nouns: who, that.

Can a complex sentence have more than one dependent clause?

Yes, absolutely! For example: “My friend who I’m renting an apartment with plays guitar because he loves it.” However, complex sentences cannot have more than one independent clause. In such cases, they are classified as compound-complex.

References

English Syntax: An Introduction by Cambridge University Press

https://www.cambridge.org/core/books/english-syntax/36746471078ADC19F555CB9198513C85

https://doi.org/10.1017/CBO9780511841675

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