Complex Sentences: Definition, Examples & How to Use Them
A complex sentence pairs an independent clause with one or more dependent (subordinate) clauses. Complex sentences let you show relationships between ideas — cause and effect, conditions, time, and contrast — creating more nuanced and sophisticated writing.
What Is a Complex Sentence?
A complex sentence has exactly one independent clause (a complete thought) and at least one dependent clause (a clause that cannot stand alone). The dependent clause begins with a subordinating conjunction or a relative pronoun.
Formula
Independent Clause + subordinating conjunction + Dependent Clause
Example: She left early because the meeting was over.
Common Subordinating Conjunctions
These words introduce dependent clauses. They signal the relationship between the main idea and the supporting idea:
Time
after, before, when, while, until, since, as soon as, once, whenever
Cause / Reason
because, since, as, now that, in order that
Contrast
although, though, even though, whereas, while
Condition
if, unless, provided that, as long as, even if, in case
20+ Complex Sentence Examples
- —Because the storm was approaching, they boarded up the windows.
- —She passed the exam although she hadn't studied much.
- —When the clock struck midnight, the guests began to leave.
- —He didn't go outside until the rain stopped.
- —If you finish your work early, you can leave.
- —While the children played, their parents talked on the porch.
- —She kept writing even though her hand was cramping.
- —Since he moved to the city, he rarely visits home.
- —Before you submit the report, check it for errors.
- —The garden flourished because she watered it every morning.
- —Although the path was steep, they reached the summit by noon.
- —Whenever I hear that song, I think of summer.
- —Unless you ask for help, no one will know you're struggling.
- —After the movie ended, we walked home in silence.
- —He smiled as if he already knew the answer.
- —The team celebrated once the final whistle blew.
- —Provided that the weather holds, the wedding will be outdoors.
- —She whispered so that no one else could hear.
- —Even though he was exhausted, he finished the last chapter.
- —As long as you believe in yourself, anything is possible.
- —The house felt empty after the children left for college.
- —Whereas her sister loved crowds, she preferred solitude.
The Comma Rule for Complex Sentences
The comma rule is simple: if the dependent clause comes first, use a comma. If the independent clause comes first, you usually do not need a comma.
Dependent clause first (comma needed)
"Because it was raining, we stayed inside."
Independent clause first (no comma)
"We stayed inside because it was raining."
Complex vs. Compound vs. Simple Sentences
Simple
"She left."
One independent clause, no dependent clause.
Compound
"She left, and he stayed."
Two independent clauses, no dependent clause.
Complex
"She left because she was tired."
One independent clause + one dependent clause.
How Complex Sentences Improve Your Writing
Using only simple or compound sentences makes prose feel flat and monotonous. Complex sentences let you:
- Show cause and effect — "He failed the test because he didn't study."
- Create suspense — "Before she opened the door, she heard a sound inside."
- Add conditions — "If the bridge holds, we can cross."
- Vary rhythm — Mixing sentence types keeps readers engaged and prevents a choppy reading experience.
- Emphasize the main idea — The independent clause carries the weight; the dependent clause provides context.
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