A complex sentence contains one independent clause and at least one dependent clause. The dependent clause can give context, describe a noun, or complete another part of the sentence.
Dependent clauses at the beginning or end
In Because the road was icy, we drove slowly, we drove slowly is the independent clause. The highlighted dependent clause tells why we drove slowly. Use a comma after this introductory clause.
The same reason can follow the main clause. We drove slowly because the road was icy. In this order, the reason clause usually follows without a comma.
Dependent clauses within the main clause
In The truck that carried the salt arrived first, the relative clause identifies which truck arrived. It is part of the subject, the truck that carried the salt, and takes no commas. In Our only truck, which carried the salt, arrived first, the relative clause adds extra information, so commas set it off.
If a sentence has a dependent clause and at least two independent clauses, it is a compound-complex sentence.
