Complex Sentences: What Is a Complex Sentence?
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Complex Sentences: What Is a Complex Sentence?
Complex sentences in English grammar are not referred to as such because they contain complex thoughts or ideas. Rather, “complex” in grammar terms concerns a sentence’s structure.
The Definition of a Complex Sentence
A complex sentence in English grammar is one that has one independent clause and at least one dependent clause.
An independent clause is one that contains a subject and a verb and that can stand alone as a sentence. Conversely, a dependent clause includes a subject and a verb but cannot stand alone as a sentence. It is made dependent by a subordinating word, and it needs to be accompanied by an independent clause to form a clear, complete expression.
Example
While I was talking to my sister, the cat ran into the front yard.
This is a complex sentence. It has an independent clause, the cat ran into the front yard, that could work as its own sentence. It also includes a dependent clause, while I was talking to my sister, that would be a fragment if left on its own. To illustrate this point, let’s separate them:
The cat ran into the front yard. (This sentence is clear and complete.)
While I was talking to my sister. (This is a sentence fragment because it represents an incomplete thought. We are left wondering what happened while you were speaking with your sister.)
Let’s look at another example:
Because I was late for work, I decided to call a taxi instead of wait for the bus.
This is a complex sentence as well. The independent clause is I decided to call a taxi instead of wait for the bus. The dependent clause is because I was late for work.
We can inspect this sentence the same way we did the first.
I decided to call a taxi instead of wait for the bus. (This sentence can stand alone as clear and complete.)
Because I was late for work. (This is a sentence fragment with an incomplete thought.)
The Value of Knowing Complex Sentence Structures
Understanding complex sentences is good for a couple of reasons. The first is to simply have a better understanding of how English is organized for precise and eloquent writing. The more you know about English grammar, the better writer and communicator you can become.
The second reason is to ensure that you are forming complex sentences where they are useful or needed while avoiding sentence fragments. Leaving dependent clauses on their own leads to choppy, unfinished prose that distracts from the points you wish to make.
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Thank you so much. I hope that you’ll share more lessons, because I want to improve my English grammar.
This is excellent! Cleft sentences can be confusing but you did a great job of explaining, as many sites do not.
Seems hard to find the subject in some of your dependent clauses.
You might find the following article helpful:
Dependent and Independent Clauses
Are the independent and dependent clauses always separated by a comma? Thanks.
Our Rules 4a and 4b of Commas state:
When starting a sentence with a dependent clause, use a comma after it.
Example: If you are not sure about this, let me know now.
But often a comma is unnecessary when the sentence starts with an independent clause followed by a dependent clause.
Example: Let me know now if you are not sure about this.
In your example “Because I was late for work, I decided to call a taxi instead of wait for the bus,” I would have written “instead of waiting for the bus…,” using a gerund object of the compound preposition “instead of.” Your use of “wait” sounds odd to me.
Your treatment is fine as a matter of stylistic preference. Our treatment is more grammatically parallel: “Because I was late for work, I decided to call a taxi instead of [to] wait for the bus.”
Either construction completes the idea, and writers could simply choose which version they think sounds better.
I decided to call a taxi instead of wait for the bus. (This sentence can stand alone as clear and complete.)
Shouldn’t it be “…instead of waiting…”?
Please see our reply of July 3, 2026, to Jan Houser.