The fourth structure combines the other two: a compound-complex sentence has two or more independent clauses (like a compound sentence) and at least one dependent clause (like a complex sentence).
Key idea
To name any structure: find every subject–verb pair, mark each as independent or dependent, then count.
Why it works
Long, rich ideas often need this structure: two main events and the time or reason that ties them together. Knowing the parts also tells you where the commas go: after an opening dependent clause, and before the conjunction that joins the independent clauses.
Worked example: A clause tucked inside
What structure is “The dog that lives next door barked, so we closed the window”?
- Independent clauses: The dog barked and we closed the window, joined by so.
- Dependent clause: that lives next door, an adjective clause inside the first independent clause.
- Two independent and one dependent.
Answer: compound-complex
Worked example: Watch for verbals
What structure is “I wanted to go, but I stayed home because I was sick”?
- I wanted and I stayed home are independent clauses; to go is an infinitive, not a clause.
- because I was sick is a dependent clause.
Answer: compound-complex
Common mistake
Miscounting when a dependent clause sits inside an independent one (“The dog that lives next door barked”), or counting a compound verb as two clauses. Mark every subject–verb pair before you count.