Punctuation marks are a convention of writing that help readers and writers more clearly understand written language. The following sections explain and exemplify the punctuation rules for using commas in numbers, dates, geographical places, personal titles, direct address, and interjections in written English.
Commas With Numbers
Use a comma to indicate thousands, millions, billions, and so on in higher numbers. Place a comma every three digits. For example:
- Our new car cost $29,000.
- The population of the United States of America is approximately 308,878,000 people.
- Milner Library owns roughly 1,500,000 volumes.
- Scientists estimate that Earth is 3,550,000,000 years old.
Do not use a comma in place of a decimal point in written American English.
Commas With Dates
Use a comma to separate the day of the week from the month, the day from the year, and the year from the rest of the sentence. For example:
- On September 11, 2001, the United States changed forever.
- Abraham Lincoln was born on Sunday, February 12, 1809, in Kentucky.
- She was born on November 26, 1920.
- The final date of the sale is Tuesday, January 3, 2010.
Do not use a comma when the day precedes the month or between months and years or seasons and years.
Commas With Geographical Places
Use a comma between street addresses and city names, city names and state names, and state names and countries. For example:
- The majority of my students are from Peoria, Illinois.
- The White House is located at 1600 Pennsylvania Avenue, Washington, DC.
- My mother-in-law once lived in Quebec, Canada.
- Bloomington, Indiana can be quite the party town.
Do not use a comma after a single part location.
Commas With Personal Titles
Use a comma to separate a personal title that follows a name. For example:
- Maria Lopez, Vice President for Finances, works in the administration building.
- Pamela Brown, M.D., is a highly reputable obstetrician.
- Martin Luther King, Jr. believed in equality.
- Marvin Cheshire, Sr. worked at the company for eighteen years.
Do not use a comma to separate a personal title that precedes a name.
Commas With Direct Address
Use a comma to separate a direct address from the rest of the sentence. For example:
- Jenny, would you please open the window?
- Do you know where the pens are, Daniel?
- Lynne, clean your room.
- You, Ms. Maggie Hovey, have won the grand prize!
Do not use a comma to separate an indirect address from the rest of the sentence.
Commas With Interjections
Use a comma to separate a brief interjection from the rest of the sentence. For example:
- The teacher said that, yes, there will be an essay question on the final exam.
- You haven't seen my new coat, have you?
- No, the café is not open on Christmas.
- The pub is having a St. Patrick's Day party, of course!
Commas perform ten basic functions in written English: separating items in a series; separating verb clauses; after adverbials and adjuncts that precede the main clause; separating coordinate adjectives; separating nonrestrictive adjective clauses; separating nonessential appositives; separating contrasted coordinate phrases; separating nonessential adverbs and parentheticals; transitioning between quotations; and in dates, geographical places, numbers, personal titles, direct addresses, and brief interjections. All writers of the English language must learn to use commas in numbers, dates, places, titles, direct address, and interjections.
For information on the other nine punctuation rules for commas in written English, please read the articles Punctuation Rules for Commas in English: Using Commas as Punctuation Marks in Written American English and More Punctuation Rules for Commas in English: When to Use Commas in Written American English.
Sources
"Commas." Purdue Online Writing Lab. Purdue University. 2010. Accessed 15 Mar. 2010.
Faigley, Lester. The Brief Penguin Handbook. New York: Pearson Longman. 2003.
Gibaldi, Joseph. MLA Handbook for Writers of Research Papers. 6th ed. New York: The Modern Language Association of America. 2003.
Heather Marie Kosur - About Me I earned a BA in English studies with a minor in creative writing from Illinois State University in May 2007 and an MS in ...
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