Many sentences start with a warm-up before the main clause: a dependent clause (an adverb clause like “When the bell rang”), a long phrase, or a single word like However or Yes. A comma marks where the warm-up ends and the main clause begins.
Key idea
Use a comma after an opening dependent clause, an opening phrase of more than a few words, or an opening word like however, yes or well. After a short opening phrase, the comma is optional.
| Opener | Comma? |
|---|---|
| When the bell rang, … | Yes: a dependent clause |
| After the long game on Saturday, … | Yes: a long phrase |
| However, … Yes, … Well, … | Yes: an opening word |
| At noon … In 2020 … | Optional: a short phrase |
Why it works
Without the comma, a reader can stumble: “While we were eating the dog barked” sounds, for a moment, as if we were eating the dog. The comma shows where the main sentence starts.
Worked example: A long opening phrase
“After the long game on Saturday afternoon we went out for pizza.”
- Find the main clause: “we went out for pizza.”
- Everything before it is an opening phrase of seven words.
- Put the comma where the opener ends, after afternoon.
Answer: After the long game on Saturday afternoon, we went out for pizza.
Worked example: The clause comes last
“We packed our bags when the bell rang.”
- The dependent clause “when the bell rang” comes after the main clause.
- At the end of a sentence, a dependent clause usually takes no comma.
Answer: No comma: “We packed our bags when the bell rang.”
Common mistake
Leaving out the comma after a long opener, so the reader trips. The opposite worry is not a mistake: after a short opening phrase, “In 2020 we moved” and “In 2020, we moved” are both standard.