We don't think about commas when we speak; natural pauses occur and we keep on talking. Unfortunately, a great many people forget about commas when they write, too. Like all punctuation marks, commas are of great assistance in any type of writing, and can easily do the following:
• Separate items in a list
• Separate two or more phrases
• Set off a phrase that is not essential to the rest of the sentence
• Set off quotes
In all cases, a comma shows a pause in the sentence, or a separation of two or more distinct ideas. Sadly, many documents and signs (both formal and informal) include either too many commas or not enough. At worst, the reader is totally confused and the original intent of the message is lost. At best, the reader must guess at the writer's meaning, based on the context of the sentence or paragraph.
For you business owners, commercial executives, or marketing advertisers, please remember that your punctuation is just as important as your spelling. If prospective customers think you've cut corners (intentionally or not) in your articles, ads, signage, or other written documents, who's to say you haven't taken shortcuts elsewhere? How can they expect to patronize your business with confidence and trust? Ensuring proper punctuation helps make your document easy to read and leaves your audience with no doubts about your message.
== Lists ==
One of the most well known uses of the comma is separating items in a list:
- I bought hats, streamers, lights, and candy for the party.
Some may argue that the last comma before the conjunction, known as the serial comma (also "Harvard comma" and "Oxford comma"), is not necessary. The sentence would therefore be read the same, but look like this:
- I bought hats, streamers, lights and candy for the party.
Depending on the style manual you use and your personal preference, this may vary. What matters most is that it makes the statement clear.
Lists can also contain phrases, not just single words:
- Laura plays the clarinet, paints nature scenes, and creates ceramic statues of Abe Lincoln.
Now just imagine if there were no commas in that last sentence. What a mess!
TIP: Always use the serial comma if the sentence is not clear without it.
== Conjunctions ==
Commas are almost always used with conjunctions, which connect words or independent clauses together. The three most popular conjunctions are "and," "but," and "or."
- The doors needed sanding, and the ceiling needed new paint.
- We can go shopping, or we can go see a movie.
If we take out one of the subjects above (in this case, the second "we"), the clause will no longer be independent. Therefore, the conjunction will not need a comma:
- We can go shopping or see a movie.
Other infrequent conjunctions are "so," "for," "nor," and "yet." You might come across the following:
- The line was moving pretty fast, so I did not wait long.
- We couldn't hear the CD, for my player had malfunctioned.
("For" is usually used in place of "because.")
- Changing occupations is difficult, yet I am doing it to make myself happy.
("Yet" is usually used in place of "however.")
When putting two independent sentences together, never use a comma without a coordinating conjunction. This is an illegal move called a comma splice:
- My computer exploded, it had too much software. [Wrong]
You can correct this easily by using either a period or a semicolon:
- My computer exploded. It had too much software.
- My computer exploded; it had too much software.
== Setting Off Words, Phrases, or Clauses ==
Sometimes you may want to expand on your idea, but you do not want to explain it with another full sentence. Introductory words or phrases, also used with commas, can be set apart from the rest of the sentence and are perfect for this scenario:
- If you build it, they will come.
- After my Las Vegas trip, I returned home with a thinner wallet!
- Hey Indiana, Jones is still on the truck.
Consider that last sentence. The writer is addressing Indiana, telling him about someone named Jones. Moving the comma, however, gives the sentence a much different meaning:
- Hey, Indiana Jones is still on the truck.
Non-essential phrases (a.k.a. parenthetical elements) are just like introductory phrases, except that they appear in the middle of a sentence. As the name implies, it is not necessary to the idea; the sentence would have the same meaning if the phrase were not there. Non-essential phrases always have commas at both ends:
- Terrence, who was always looking for treasure, loved to go to the beach.
- The snowfall, which lasted for three days, completely covered my car!
- The case is closed, according to my partner, and will be placed in the archives.
And lastly, concluding words or phrases do the same exact thing, but they are placed—yep, you guessed it—at the end of a sentence, always with a comma:
- He became a firefighter to help people, especially older folks.
- That's a funny situation, if you think about it.
- I saw Jerry Seinfeld at the Kennedy Center, a beautiful performance venue.
== Coordinate Adjectives ==
Depending on your priorities, you may want to give equal importance to multiple adjectives that describe the same noun (allowing their order to be switched). These are called coordinate adjectives, and they always have a comma after each, except the last one. For instance:
- The new, shiny desk was made of oak.
- The shiny, new desk was made of oak.
- Some people insist that ferrets make funny, cute pets.
- Some people insist that ferrets make cute, funny pets.
- Dressing a fussy child is like wrestling with an obstinate, angry octopus.
- Dressing a fussy child is like wrestling with an angry, obstinate octopus.
TIP: Use only one adjective at a time, two only if necessary. Any more than that and your message will become less believable to your readers.
== Quotes ==
Setting off quotations is one of the most well-known, yet trickiest uses of the comma. Don't forget that in the United States, commas and periods finishing the quote are placed inside the quotation marks (as opposed to the more logical British writing, where the commas and periods are outside.) The following examples are American:
- "My friend will have the Chicken Cacciatore," I told the waiter.
- Gina came inside and said, "They've started the puppet show."
Commas are also used when the quote is split:
- "I went to the lobby," said Paul, "but my mother was in the casino."
TIP: Write with your audience in mind. Knowing the differences between American English and British English will help you use punctuation consistently and avoid confusing your audience. By the same token, when reading, comma placement can be a clue about the nationality of the author. If you surmise that s/he is not from your home country, you'll have a better chance of also realizing that his/her word meanings may be different than what you are used to. Keep an open mind.
== Summary ==
In the most basic terms, commas should help create understandable writing. Remember to use commas to separate list items and avoid comma splices. Set off an unnecessary phrase at the beginning, middle, or end of a sentence. If it still makes sense without the non-essential phrase, you've used your comma well. Lastly, always proofread.
For more detailed, easy-to-read help with commas, visit: