Writing · Free lesson
Put the comma after the whole introductory clause
You are writing about the start of a museum visit. The opening part tells us when the main action happened. Mark the boundary between those two parts.
Professor Scott MendozaThe short answer
Place a comma after the complete introductory dependent clause: “After the doors opened, the visitors entered.” The comma comes after opened, not immediately after After or between the visitors and entered.
Finish the opening clause before you punctuate it.
After the doors opened has its own subject and verb, but after makes it dependent on a main clause. The visitors entered can stand alone. A comma separates the introductory clause from that main clause.
Locate the boundary
After the doors opened, the visitors entered.
When the guide arrived, we started the tour.
We started the tour when the guide arrived.
Do not put a comma between the main subject and its verb: “the visitors, entered” splits a unit that belongs together.
Separate the two clauses
Find the opening time clause
When the guide arrived, ...
Keep the main clause together
... we started the tour.
Try it now
Choose the comma position
Read all answers and explanations
Choose the standard punctuation for this introductory clause.
After the doors opened, the visitors entered.The opening clause ends after opened. After alone is not the whole clause; visitors and entered must stay together.
Where does the introductory clause end in “Before we leave we should check the map”?
Before we leave, we should check the map.Before we leave is the whole opening clause. The main subject we stays with should check.
Choose normal punctuation when this simple time clause follows the main clause.
We started the tour when the guide arrived.No comma is needed in this version. Do not separate we from started or started from its object.
Put it into practice
Fix the tour note
Keep the word order and add one comma after the complete opening clause.
When the guide arrived we started the tour.
See a model answer
When the guide arrived, we started the tour.
One boundary comma makes the sentence easier to follow.
A little more clarity
Common questions
A few useful details before you move on.
Should I add a comma whenever I pause?
No. A speaking pause is not a reliable punctuation rule. Identify the sentence structure first.
When the doors opened, everyone entered.
Can the introductory clause be a separate sentence here?
Not as a complete statement in this structure. When the guide arrived needs a main clause to finish the message.
When the guide arrived, we started the tour.
Take it into your day
Put the comma at the end of the opening clause, not inside the main subject–verb pair.
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