Compound-Complex Sentence

1. What is a Compound-Complex Sentence?

Compound-complex sentences are the most complicated sentences, like the name implies. A compound-complex sentence has at least two independent clauses and at least one dependent clause. In simple terms, an independent clause can be a sentence on its own while a dependent clause cannot be a complete sentence.

Compound-complex sentences let us express longer thoughts, with more parts than other sentences let us use. They’re good tools for explaining complicated ideas or describing long chains of events.


2. Examples of compound-complex sentences

Compound-complex sentences are surprisingly common. You probably see them a lot in books that you read for school, and even in books that you read for fun. Here are some examples to help you understand what makes a sentence a compound-complex sentence.

Example 1

            Kate doesn’t like cartoons because they are loud, so she doesn’t watch them.

This sentence has two independent clauses and one dependent clause. The dependent clause “because they are loud” can’t be a complete sentence on its own, and that’s what makes it dependent. As you’ve probably figured out, the independent clauses “Kate doesn’t like cartoons” and “she doesn’t watch them” can be complete sentences on their own.

Example 2

            The dog started barking so the cat ran away and I couldn’t keep up, so I stopped.

Now we’re dealing with more clauses, but they still follow the same rules. The independent clauses can still be complete sentences, while the dependent clause is an incomplete sentence fragment.

Both of these examples have little words called conjunctions that link up the clauses. Read on to the next section to find out more about conjunctions and the other parts of a compound-complex sentence.


3. Parts of Compound-Complex Sentences

Compound-complex sentences are the most complicated sentences, but once you know how to look for the separate parts it gets easier to understand them. We already know the basic rules: there must be at least two independent clauses and at least one dependent clause. There are a few more things you have to know, and then you’ll be ready to write compound-complex sentences without a problem!

a. Independent Clause

An independent clause will always be able to stand on its own as a complete sentence. That means it has a subject and a predicate. The subject of the clause will be a noun and the predicate will describe the subject or what the subject is doing.

The independent clauses in a compound-complex sentence are called coordinate. This is a fancy way to say that they’re related to each other, and that it makes sense for them to be in the same sentence.

Here are a few examples of independent clauses in compound-complex sentences, with the independent clauses highlighted in green. You can see that they’re related to each other because they have to do with the same subject, and that they can be complete sentences.

  • Even though she was tired, Abby knew she had to finish the race, so she ran to meet her team.
  • Usually I take a walk every day while the sun sets, but it was raining today.
  • She likes to sleep in but she can get up early if she has work.

The parts of these sentences that aren’t blue are either dependent clauses or conjunctions. We’ll learn more about conjunctions soon, and dependent clauses even sooner!

b. Dependent Clause

The dependent clauses in compound-complex sentences will not be complete sentences on their own. They are dependent on the other clauses of the sentence, because they don’t have a full meaning without more information. Even though dependent clauses have a subject and a predicate like independent clauses, dependent clauses don’t express a full thought.

We’ll use the same examples from earlier to show you dependent clauses. In general, dependent clauses are phrases that add more information to a compound-complex sentence.

Example 1

Even though she was tired, Abby knew she had to finish the race, so she ran to meet her team.

In the first sentence, the dependent clause “Even though she was tired” tells us why Abby was having trouble finishing the race. The clause is also introduced by “Even though,” which is a subordinating conjunction (you’ll learn about this in the next section). For now, let’s take a closer look at the second example sentence to see how dependent clauses give us more information.

Example 2

Usually I take a walk every day while the sun sets, but it was raining today.

Like before, the independent clauses are green and the dependent clause is orange. If we take out “while the sun sets” we can see that this isn’t a complete sentence. But it does give us some interesting information about when I take walks! It answers the question of when, and it is also introduced by the subordinating word “when.” By giving us the time that the walks are taken, the dependent clause tells us more about the situation. Even though we could take out the whole phrase and still have a correct sentence, we would have less information and a less interesting sentence.

c. Conjunction

Conjunctions are those little connecting words that let us put sentence parts together. In compound-complex sentences, we use conjunctions to string together all of our independent and dependent clauses. The most common conjunctions are and, or, and but.

There are different types of conjunctions that do different things, and there are more kinds of conjunctions than those covered here, but these are the important ones for compound-complex sentences.

Coordinating conjunction

Coordinating conjunctions connect independent clauses and other short phrases. There are seven coordinating conjunctions, and you can remember them using the acronym FANBOYS.

F – for

A – and

N – nor

B – but

O – or

Y – yet

S – so

Simple enough, right? You’ll use the FANBOYS to connect two or more independent clauses in compound-complex sentences. Here’s an example from our earlier sentences.

Example 1

            She likes to sleep in but she can get up early if she has work.

We’ve got a big, purple but in there: that’s our conjunction! It links the two independent clauses in green so that we know they’re coordinate clauses and belong in the same sentence.

Subordinating conjunction

A subordinating conjunction introduces a dependent clause, so you can see how these would be useful in compound-complex sentences. There are a lot of subordinating conjunctions, but some common ones are if, while, and though. Let’s use the same example as above.

Example 1

            She likes to sleep in but she can get up early if she has work.

In this example our conjunction is if. It introduces the dependent clause if she has work and it is part of the clause too. It subordinates the clause making it dependent.


4. How to Write Compound-Complex Sentences

So now you’re familiar with the parts of compound-complex sentences, and it’s time to start putting them together. This is as easy as coming up with two sentences and one extra bit of information, and then using conjunctions to link them all up. I bet you’re tired of those older example sentences, so let’s create a brand new one to show how they’re made.

Step 1: Independent clause

The first independent clause of your compound-complex sentence should have a strong main idea. It doesn’t have to come first in your final sentence, but you’ll need a guiding idea to get you started. Let’s say I want to write a sentence about a cat. My independent clause might look like this:

The cat jumped onto the couch.

This is a complete sentence all on its own, which is how we know it’s a good independent clause for our complex-compound sentence.

Step 2: Related independent clause

Now we need another independent clause that is related to the first independent clause. Sometimes this means the clause will have the same subject, or use a word that’s in the other independent clause. The new clause should continue the action or add new information.

The sun shone onto the couch.

This is another complete sentence, and it mentions the couch from the first independent clause. Now we’re ready for a dependent clause.

Step 3: Dependent clause

Our dependent clause will spice up the two independent clauses that we’ve already written. It could tell us more about the situation or explain an action, but it can’t be a complete sentence on its own. Here’s a dependent clause about the cat and the couch:

made it warm

Clearly, this is only part of a sentence, but it tells us that something is being warmed up by something else. When we stick it in the right place and add the right conjunctions, it’ll make much more sense.

Step 4: Put it together with conjunctions

Let’s gather all of our clauses and decide on an order.

  • The sun shone onto the couch.
  • made it warm
  • The cat jumped onto the couch.

This might look like nonsense now, but let’s dig into our big box of conjunctions and pull out which and so. These will help us put everything together into a compound-complex sentence.

The sun shone onto the couch, which made it warm, so the cat jumped onto the couch.

And there it is: a compound-complex sentence! We have our two independent clauses, one dependent clause, and conjunctions that link everything together. When you’re out making your own compound-complex sentences, you can use more clauses than this as long as people can still follow the sentence. That brings us into our next section about how to write the best compound-complex sentences you can.


5. Avoiding Run-on Sentences and Comma Splices

A run-on sentence has two or more independent clauses but doesn’t use the right punctuation or linking words to connect its clauses. That means that even very short sentences can be run-ons. You’ll be in more danger of using run-on sentences with your long compound-complex sentences, so keep a sharp eye out.

Example 1

The temperature has dropped, it’s windy outside, wear a jacket.

Even though these are related, they’re not connected in the right way. When two independent clauses are only connected by a comma, it’s called a comma splice. There has to be a connecting word or different punctuation for this sentence to be correct. See the next examples for different ways to fix this sentence.

Example 2

The temperature has dropped and it’s windy outside, so wear a jacket.

Now we’ve got a nice connecting words to prevent a comma splice! The conjunction “and” connects the clauses and makes this a proper sentence. Meanwhile, the subordinating conjunction “so,” turns the clause “wear a jacket” into a dependent clause.

Example 3

The temperature has dropped; tt’s windy outside; wear a jacket.

Using a semicolon allows us to connect the clauses without adding an extra word, and we can still follow grammar rules to avoid comma splices.

Compound-complex sentences will seem less complicated as you get more practice with them, and then they become a great tool for explaining longer ideas. Knowing more about the different sentence types will also help you spice up your writing and show off your skills!

Test your Knowledge

TRUE or FALSE: A compound-complex sentence has to have at least three independent clauses.



What do conjunctions do in a compound-complex sentence?





Which is the dependent clause in this sentence?

When the sky is cloudy, I like to sit outside and sometimes I read a book.





What kind of conjunction is 'and' in the sentence found in Question 3?





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