A comma functions like yield signs, a pause to keep you from having a wreck, crashing into the words ahead.
- Show a pause …
after an introductory phrase longer than three or four words.
- If you want to keep the meaning clear, pause after a long opening phrase.
- For short openers you might not want to pause. (No comma needed).
to separate a question from a statement.
- Bill is coming, isn’t he? (Notice the natural pause after “coming,” which keeps the statement from running into the question.)
- I can’t believe that, can you?
to separate a list of three or more items.
- In the pantry Johnny found the bread, peanut butter, and grape jelly. (Some style books want to leave out the comma before the conjunction, but that can be confusing.)
- A soldier’s favorite colors should be red, white, and blue.
in place of saying “and” between two adjectives that modify a noun.
- John is a kind, intelligent young man.
- He stared vacantly into the clear, clear blue sky. (If saying “clear and blue sky” sounds awkward to you, don’t use a comma.)
for dialogue attributions that voice the words.
- “I’ve got a secret,” Sammie whispered.
- Patty laughed, laughed. “She looks ridiculous in plaid dress.” (People don’t laugh words, they say them. The laughter needs to be a separate sentence.)
to change the sound and pace of the sentence.
- Timmy counted eight-nine-ten and ran to find where his friend was hiding. (Quick count, using hyphens instead of commas).
- Mom counted one, two, three, and Timmy jumped up from the TV and went to take his bath. (Slow count).
- Show pauses surrounding …
an emphasized adverb.
- We waited, patiently, for our son to get home. (The emphasis suggests an involuntary choice.)
a phrase that doesn’t restrict what it modifies.
- Peter, who graduates this year, plans to join the army. (“Who graduates this year” doesn’t limit the meaning of Peter. Leave out the phrase and the sentence is still true, so a comma should be used.)
- A man who wishes he had a friend isn’t very friendly. (“Who wishes he had a friend” limits the identity of “the man.” Leave out the phrase and the meaning changes, so a comma should not be used.)
an interrupting phrase or word.
- I believe, no matter what the weather is like, we’ll have a good time.
- When I’m writing, honestly, I’m in another world. (Without the comas, you have to wonder what it’s like to write dishonestly.)
the name or title of someone addressed directly.
- Listen, Jack, you don’t have a job if you can’t get here on time.
- That, sir, is the whole story.
the year when it follows the month and day.
- On August 11, 1984, President Ronald Reagan joked about bombing Russia.
- Garry Kasparov faced IBM’s chess-playing computer in February 1996 and won. (Without the day, no commas are needed to set of the year.)
degrees or titles that follow names.
- William Henry, M.D., did the surgery.
- Jack Moncrief Jr built a financial empire. (“Jr” and “Sr” are now considered a part of the name. Commas and period are no longer required.)
- Next to Quotation Marks.
Unlike colons and semicolons, which always go outside, the comma always goes inside the quotation marks.
Example: After so many days reading “How to Write,” I just needed to write.