Complex Sentences
Complexity here is structural, not a judgment that the sentence is long or difficult. Dependent clauses can function as adverbial, relative, or content/noun clauses, and they can appear before, after, or within the main clause.
A complex sentence contains one main/independent clause and at least one subordinate/dependent clause. “We stayed inside because it was raining” is complex because “we stayed inside” can stand alone but “because it was raining” depends on it.
Key details
Further guidance
Clause Types
A dependent clause may express time, reason, condition, description, reported content, or another subordinate relationship.
Diagnostic
Find the clause that can stand as the main clause, then identify one or more subordinate clauses that depend on it.
Punctuation
Punctuation depends on the clause type and position; do not use “complex sentence” as a shortcut for one comma rule.
Worked Example
“Although the train was late, we arrived before noon” is complex: “we arrived before noon” is the main clause and “although the train was late” is subordinate.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Complex sentence (opens in a new tab)Cambridge University Press · Defines a complex sentence as containing a main part plus one or more additional clause parts, with examples describing an independent clause and subordinate clause.
- Clauses (opens in a new tab)Cambridge University Press · Distinguishes main/independent from subordinate/dependent clauses and shows how they combine, supporting a bounded complex-sentence construction guide.