Have you ever written a sentence that follows the grammar rules but somehow doesn’t feel right? It was likely missing a complex sentence or two.
A complex sentence is one of the most versatile and important parts of the English language. It helps you to create connections between ideas, highlights cause and effect, provides context, and makes your sentence sound like a complete speech rather than a series of short, clumsy sentences.
In this article, we will provide all the information you need about what a complex sentence is, how to construct one, how it differs from a compound sentence, and how to use proper punctuation, with many practical examples.
What Is a Complex Sentence?
A complex sentence consists of an independent clause and at least one dependent clause joined by a subordinating conjunction such as ‘because’, ‘if’, ‘since’, ‘although’, or ‘when’.
To put it simply, a complex sentence is a combination of a full sentence with some additional information depending on it.
For example:
Because it started raining, we decided not to go to the church.
Explanation:
In the sentence above, ‘because it started raining’ is a dependent clause. It provides information; however, it cannot be used as an independent clause. On the other hand, ‘we decided not to go to the church’ is the independent clause. It is a complete sentence.
Complex sentences are found in every kind of communication, like email, essay, and article, because they allow us to convey the relationships between different ideas (cause, condition, contrast, time).
Independent Clauses vs. Dependent Clauses
Understanding complex sentences requires knowledge about two types of clauses that are used in their construction: independent and dependent clauses.
Quick comparison:
| Independent Clause | Dependent clause |
| Contains a subject and a verb | Contains a subject and a verb |
| Expresses a complete thought | Does not express a complete thought |
| May be used as a separate sentence | Cannot be used as a separate sentence and depends on an independent clause |
For example:
- Independent clause: She finished the work report early.
- Dependent clause: Because she finished the work report early…
Take note of how the above dependent clause seems incomplete. What comes after ‘because she finished the work early?’ It requires an independent clause to finish the statement:
“Because she finished the work report early, she quickly left the office.”
The simplest way to identify a dependent clause would be to look for a subordinating conjunction at the beginning of the clause (because, since, when, although, while, if, unless, until, and others like them).
A good trick: Try to read the clause alone. If it seems incomplete, as if it needs to be finished, then it is a dependent clause.
Complex Sentences vs. Simple and Compound Sentences
In English grammar, sentences can be classified into four different types, and it is useful to look at where a complex sentence stands among other types of sentences.
Simple sentence: It consists of one independent clause only and nothing more.
Example: The dog barked.
Compound Sentence: More than one independent clause, and the clauses are combined using a coordinating conjunction (for, and, nor, but, or, yet, so), mainly known as the FANBOYS acronym.
Example: The dog barked, so the children ran away.
Complex sentence: In this type of sentence, at least one independent clause is combined with one dependent clause using a subordinating conjunction.
Example: Even though the dog barked, the children did not run.
Compound-complex sentence: This type of mixed sentence has two independent and one dependent clause. (Details in the next section)
Important notice: A compound sentence joins two complete ideas of equal significance. A complex sentence joins one complete idea with another one that supports the main idea. It is the nature of the relation between an idea and its supporting clause that makes complex sentences descriptive.
What Is a Compound-Complex Sentence?
After getting familiar with the complex sentence, it is also important to be acquainted with another more elaborate form: the compound-complex sentence.
A compound-complex sentence includes at least two independent clauses and at least one dependent clause. Essentially, it is a compound sentence but with an additional dependent clause.
For example: Although I was exhausted, I completed the timesheet, and I sent it before the submission time.
Explanation:
1. Dependent Clause: ‘Although I was tired’
2. Independent Clause: ‘I completed the timesheet’
3. Independent Clause: ‘I sent it before the submission time’ (connected to the first clause by ‘and’)
This is where several skilled writers also get confused because a compound-complex sentence may be somewhat similar to a complex sentence. How do you tell the difference? Count the number of independent clauses in the sentence. If there are two or more independent clauses and a dependent clause, then it is a compound-complex sentence.
Common Subordinating Conjunctions and What They Express
Subordinating conjunctions are the terms that make the independent clause into a dependent one. Moreover, they indicate the connection between the clauses. This is how they can be grouped according to their function:
| Subordinating Conjunctions | Example |
| Cause and effect (since, as) | Since the shop was closed, we got our meals delivered. |
| Time (when, while, before, after, until, as soon as) | After the meeting ended, everybody went for a break. |
| Condition (if, unless, provided that) | You will fail the test unless you start studying. |
| Contrast (although, though, whereas, even though) | Even though the question paper was lengthy, I answered every question. |
| Purpose (so that, in order that) | I left home early so that I could catch the bus on time. |
Knowing how to identify these words is perhaps one of the quickest ways to be able to detect a complex sentence, and when a sentence begins with one of these words, you are definitely dealing with a dependent clause.
Comma Rules for Complex Sentences
Comma placement in a complex sentence will entirely depend on the position of the dependent clause relative to the independent clause. In other words, there is a single rule here, but it can be applied in two directions.
Rule 1: Dependent clause first means a comma is needed.
If the dependent clause is placed at the beginning, a comma should be placed right after it before the independent clause starts.
Example: Because her car broke down, she arrived late.
Rule 2: Independent clause first – Usually no comma
If the independent clause precedes the dependent one, no comma is needed in most cases.
Example: She arrived late because her car broke down.
Using the same two clauses and the same subordinating conjunction, the only difference between them is their order, and the comma goes according to that order.
The only exception worth remembering is that if the dependent clause at the end of the sentence is contrasting (introduced by words like as, although, or even though), then it is possible to use a comma for clarity, though the clause follows the independent one.
Example: I decided to go for a run, even though it was raining.
In case of doubts, try reading the sentence aloud. If there is a natural pause at the junction of two clauses, the comma is required there.
Common Mistakes: Sentence Fragments and Misplaced Commas
It is common to make certain mistakes in writing complex sentences, especially when you are learning it. We have listed the two errors that need to be avoided at any cost.
Error #1: Leaving a dependent clause alone
Example: Because she was running late.
It results in a sentence fragment that consists of only a part of a sentence but is punctuated as a complete sentence.
It isn’t a sentence since it fails to inform the reader about what transpired. The error should be corrected by adding an independent clause.
Correct sentence: Because she was running late, she skipped breakfast.
Error #2: inserting a comma before the conjunction when the independent clause is placed first.
Example: I skipped breakfast, because I was running late.
A comma splice occurs when an unnecessary comma is placed, as in the sentence above it isn’t required. In this case, the independent clause precedes the dependent clause.
Correct sentence: I skipped breakfast because I was running late.
One easy method to spot the two errors: try reading each clause separately. If the first part sounds incomplete without the other, you have a dependent clause and can easily tell if a comma should be used or not depending on the position of the clause.
Examples of Complex Sentences in Everyday Writing
A complex sentence is not only part of grammar class but also an aspect that appears often in the writing that you do every day. Here are some examples in various settings:
- Corporate email: If you get the job done ahead of schedule, you can go home early.
- Personal story: As the coffee was brewing, I started doing the laundry.
- Travel writing: Since the plane was canceled, we decided to stay in Munich for another week.
- Blog entry: Even though the recipe seemed hard, it was not as difficult as expected.
- News article: After they saw the results, the group cheered.
Can you see how in each case, there is added information, such as a reason, condition, context, or contrast? This is why it is important to learn to use complex sentences because they help make your writing sound more natural and fluid.
Frequently Asked Questions About Complex Sentences
What is a complex sentence?
A complex sentence is a sentence that contains one independent clause and at least one dependent clause linked together through a subordinating conjunction like ‘because’, ‘although’ and ‘when’.
What is the difference between an independent clause and a dependent clause?
An independent clause can be used as a sentence, whereas a dependent clause cannot be because it needs to link with an independent clause to make sense.
What is the difference between a complex sentence and a compound sentence?
A compound sentence links two independent clauses through a coordinating conjunction, while a complex sentence links an independent and dependent clause through a subordinating conjunction.
When should you use a comma in a complex sentence?
A comma should be placed after the dependent clause if the dependent clause comes first in the sentence, but when the independent clause comes first, then a comma is unnecessary before the dependent clause.
What is a compound-complex sentence?
A compound-complex sentence is made of at least two independent clauses and at least one dependent clause.
