A subordinating conjunction introduces a dependent clause and signals how it relates to the main clause. In We turned back because the trail was icy, because introduces the reason we turned back.
Common subordinating conjunctions
- Reason. We took the bus because the ferry was full.
- Time. When the ferry arrived, we boarded.
- Condition. If the trail is clear, we can keep going.
- Concession. Although it was late, we finished the walk.
- Purpose. We left early so that we could catch the ferry.
Where the comma goes
Use a comma after an introductory adverbial clause. Compare Because the trail was icy, we turned back with We turned back because the trail was icy. A reason clause that follows the main clause usually takes no comma. See complex sentence for more clause patterns.
