Commas with compound and complex sentences
Key Notes:
In a compound sentence, use a comma before the coordinating conjunction that joins the two independent clauses. Examples of coordinating conjunctions are and, or, but and so.
- We saw a flash of lightning, and seconds later we heard the rumble of thunder.
In a complex sentence, if a dependent (or subordinate) clause comes before an independent (or main) clause, use a comma after the dependent clause. A dependent clause is one that starts with a subordinating conjunction, such as after, although, as, because, before, if, since, unless, until, when or while.
- If she ever gets the chance, Terri would love to visit the Egyptian pyramids.
Learn with an example
Correct the text by inserting one comma.
,
- You may need a crown on your damaged tooth or you might require a root canal.
This is a compound sentence, so use a comma before the coordinating conjunction or, which joins the two independent clauses.
You may need a crown on your damaged tooth, or you might require a root canal.
Correct the text by inserting one comma.
,
- The restaurant received a huge delivery of seafood so the chef was inspired to create an entrée of pecan-encrusted sea bass.
This is a compound sentence, so use a comma before the coordinating conjunction so, which joins the two independent clauses.
The restaurant received a huge delivery of seafood, so the chef was inspired to create an entrée of pecan-encrusted sea bass.
Correct the text by inserting one comma.
,
- Because reliable evidence in the case of Jack the Ripper is scarce the true identity of the nineteenth-century killer remains a mystery.
This is a complex sentence in which a dependent clause comes before an independent clause. You can tell because the first clause starts with a subordinating conjunction, because. Use a comma after the dependent clause.
Because reliable evidence in the case of Jack the Ripper is scarce, the true identity of the nineteenth-century killer remains a mystery.
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