A complex sentence combines one independent clause (a complete thought that can stand alone) with at least one dependent clause (a group of words that has a subject and verb but can’t stand on its own). Here’s a straightforward example: “Although our tent was zipped up, the sound of hyenas in the distance still frightened us.” The dependent clause is “Although our tent was zipped up,” and the independent clause is “the sound of hyenas in the distance still frightened us.”
What Makes a Sentence Complex
The key ingredient is a dependent clause, which is created by a subordinating conjunction. Words like “because,” “although,” “when,” “if,” “since,” “before,” “unless,” “while,” and “even though” all turn what would otherwise be a complete sentence into a dependent clause. That dependent clause then attaches to an independent clause, and together they form a complex sentence.
Take the clause “we buy his birthday cake.” That’s a complete sentence on its own. But add “when” to the front and it becomes “when we buy his birthday cake,” which now feels incomplete. It needs something else to finish the thought: “When we buy his birthday cake, we have to make sure it’s lemon.” That’s a complex sentence.
More Examples Broken Down
A complex sentence can put the dependent clause first or last. Both arrangements work:
- Dependent clause first: “When we buy his birthday cake, we have to make sure it’s lemon.” The dependent clause is “When we buy his birthday cake.”
- Dependent clause last: “The sound of hyenas in the distance frightened us even though our tent was zipped up.” The dependent clause is “even though our tent was zipped up.”
A complex sentence can also have more than one dependent clause. “When we buy his birthday cake, we have to make sure it’s lemon, because it’s his favorite” has two dependent clauses (“When we buy his birthday cake” and “because it’s his favorite”) attached to one independent clause.
The Comma Rule
When the dependent clause comes first, place a comma after it: “Although she studied all night, she still felt nervous about the exam.” When the independent clause comes first, you typically skip the comma: “She still felt nervous about the exam although she studied all night.” The exception is when the two clauses express a sharp contrast, in which case a comma before the dependent clause is appropriate.
How Complex Differs From Compound
A compound sentence joins two independent clauses with a coordinating conjunction. The easy way to remember coordinating conjunctions is the acronym FANBOYS: for, and, nor, but, or, yet, so. In a compound sentence, both halves could stand alone as complete sentences. “I studied all night, and I aced the test” is compound because “I studied all night” and “I aced the test” are both independent clauses linked by “and.”
A complex sentence, by contrast, always has one clause that depends on the other. “Because I studied all night, I aced the test” is complex. “Because I studied all night” can’t stand on its own. If you can spot a subordinating conjunction (because, although, when, if, since, unless, while, before, after, even though, until, whereas, wherever, and others), you’re looking at a dependent clause, and the sentence is complex.
Quick Test for Any Sentence
To figure out whether a sentence is complex, try this: find the conjunction. If it’s a FANBOYS word connecting two complete thoughts, the sentence is compound. If it’s a subordinating conjunction like “because” or “although,” you have a dependent clause, which makes the sentence complex. If there’s no dependent clause and no coordinating conjunction joining two independent clauses, you’re probably looking at a simple sentence.