How should I use a comma with a subordinate clause?

Subordinate clauses are sentence fragments that start with a subordinating conjunction (e.g. after, although, as, as if, as long as). They can't form a sentence on their own, but they add information to the main clause, usually some form of condition, e.g. if you do this, whenever you see him.

Subordinate clauses are great because they add variety to your writing, but often, writers are not sure how to use commas with them. A missed comma after a subordinate clause is one of the most common mistakes that we see. So how do you punctuate a subordinate clause? It turns out there is a pretty simple rule:

If a subordinate clause comes before the clause it is attached to then it should be followed by a comma. You do not need a comma before a subordinate clause if it follows the main clause (except "whereas" and "although").

Here's one example:

• Correct: If you're ready, we can begin.
• Correct: We can begin if you're ready.
• Incorrect: If you're ready we can begin.
• Incorrect: We can begin, if you're ready.

Here's another example:

• Correct: Although you're ready, we must wait.
• Correct: We must wait although you're ready.
• Incorrect: Although you're ready we must wait.
• Incorrect: We must wait, although you're ready.