The most common and most misunderstood punctuation mark must be the comma, yet it needn't cause headaches if we keep its basic function in mind. In fact, the common statement, "I use a comma whenever I want a pause in my sentence," shows a good understanding of comma use: to identify word groups and mark divisions within the sentence.
Because we often intuit or "hear" these divisions, we naturally pause for an instant. An ear for these language rhythms can help, but it isn't enough. Because readers expect commas to appear at certain points in a sentence, some comma uses must be learned. When you can apply these four rules and supplement them with your intuition, you'll know all you need to know about commas.
When you can apply these four rules and supplement them with your intuition, you'll know all you need to know about commas.
1. Use a comma before a coordinating conjunction that joins independent clauses.
This rule's meaning should be clear from our discussion of Basic Sentence Concepts. The rule is easy to understand and follow, yet failure to observe it accounts for about one-third of all comma errors. In a sentence like the following, a comma goes before the conjunction that marks the important division in thought:
|Nadine hit a high pop-up and the pitcher caught it.|
|Nadine hit a high pop-up, and the pitcher caught it.|
The comma helps readers see the main division of thought, and in doing so keeps them from momentarily thinking Nadine hit "a high pop-up" and "the pitcher." Sometimes in a sentence this short, no comma is needed, but as in the sentence above, a comma can often make the meaning immediately apparent. Notice, this rule doesn't ask for a comma before every coordinating conjunction, just those that connect independent clauses.
2. Use a comma to set off introductory elements, especially those that contain a verb or a verb form.
As this present sentence shows, a writer will sometimes hold back the subject of a sentence for a moment, leading up to it with an introductory phrase or clause. Putting a comma at the point where the introductory element ends and the main clause begins signals your readers that they've come to the start of the base clause and prevents them from running the two elements together.
When she finally swung Nadine hit a high pop-up, and the pitcher caught it.
When she finally swung, Nadine hit a high pop-up, and the pitcher caught it.
That slight pause before "Nadine," lets readers see that "Nadine" begins a new thought unit, the base clause. Even shorter introductory elements should be set off with commas if they contain a verb or verb form.
|Swinging fiercely Nadine hit a high pop-up, and the pitcher caught it.|
|Swinging fiercely, Nadine hit a high pop-up, and the pitcher caught it.|
"Swinging" is a verb form, a participle. Another verb form commonly found in introductory elements in the infinitive:
To cap it off, Nadine hit a high pop-up, and the pitcher caught it.
"To cap" is the infinitive. Always separate these participial and infinitive phrases from the base clause with a comma.
When the introductory element contains no verb or verb form, use your own judgment based partly on the length of the introductory element and partly on how closely you want to connect it with the base clause.
In the last inning Nadine hit a high pop-up, and the pitcher caught it.
In the last inning of the final game of the season, Nadine hit a high pop-up, and the pitcher caught it.
In the first example above, the introductory phrase is short and contains no verb or verb form. It could be set off or not, at the writer's preference. The element introducing the second sentence, however, is longer, and a comma signals the reader's short-term memory to process the information before going on to the main clause.
3. Use commas to set an interrupting element off from the rest of the sentence.
Of our four rules, this one, because it covers a variety of grammatical situations, is hardest to explain. Fortunately, in most situations, as right now, you can pick the interruption up with your ear, which senses that something has been inserted into the sentence, breaking the rhythmic flow. A comma helps the reader to sense this interruption as something separate from, something inserted into, the rest of the sentence, a kind of supplementary comment.
One common kind of interrupter is a clause, a phrase, or even a single word that adds incidental information about a more basic sentence element. Usually the interrupter comes right after the element it modifies.
If, as sometimes happens, you are unsure whether a modifier is restrictive or not, trust your ear. Listen for a pause.
Does your ear detect the interrupter in the following example?
My uncle Ben who showed me this spot is quite a fisherman.
If you can also recognize that "who showed me this spot" adds information about Ben without selecting him from a larger group, then you can see why the information is considered incidental, or non-restrictive, and why the element is considered an interruption. Now try to hear an interruption in the following sentence:
The man who showed me this spot is quite a fisherman.
The natural pause disappears, and with it the need for commas, because "who showed me this spot" is no longer incidental information. Now "who showed me this spot" selects from a large number of possible men the one man being talked about. In other words, it restricts the meaning of the word it modifies. That's why the pause disappears and also why no commas are needed to set the expression off.
Single-word modifiers can also be restrictive or non-restrictive and are treated the same as restrictive and non-restrictive clauses.
Marvin, my brother, plays a wicked sax.
My brother Marvin plays a wicked sax.
In the first sentence, "my brother" adds extra information about Marvin and therefore needs to be set off. The second sentence doesn't need commas because "Marvin" selects from all possible brothers the one being talked about and is therefore restrictive. If, as sometimes happens, you are unsure whether a modifier is restrictive or not, trust your ear. Listen for a pause.
Other incidental interrupters that should be set off with commas are easy to identify and seldom cause trouble. The most common are: "yes" and "no":
Yes, I'd love a lemonade.
Names of people spoken to:
I'm afraid, my friend, that it's all gone.
And miscellaneous words and phrases moved out of a more natural word order:
This, for a thirsty pilgrim, was unwelcome news.
4. Use a comma to separate items in a series.
This rule is easy to understand and follow. The series below would be punctuated correctly by almost everyone:
Plowing, planting, and harvesting were our biggest jobs.
The Yankees finished ahead of the Tigers, the Red Sox, and the Indians last year.
Some you win, some you lose, and some get rained out.
Another simple kind of series is a series of place-names:
Bartlesville, Oklahoma, is where I learned to use chopsticks.
A sequence of dates can also be treated as a series:
Friday, September 29, 1928, was a bad day for investors.
Finally, a series of adjectives modifying a single base word should be separated with commas unless the words are frequently paired:
That tattered, faded couch had become a good friend.
I found it in a quiet little village by the sea..
A Final Word on Commas
The four rules above will cover almost all situations; however, when a situation isn't clearly covered by any rule, two more guidelines may help.
1. Use a comma to prevent possible misreadings.
|What he had done told more about him than what he said.|
|to:||What he had done, told more about him than what he said.|
2. When in doubt, leave it out.
This explains itself. Over-punctuation can cause confusion as easily as under-punctuation. If you can't think of a good reason to use a comma, you probably shouldn't.
4.18 Using the four guidelines you just studied, supply commas wherever needed in the following sentences. Some sentences may not need to be changed at all. Others may need to have commas removed.
a. From some of the most remote parts of the country people came to the inauguration.
b. Many are called but few, are chosen.
c. What will you do with a rusted dilapidated car like that?
d. If you ever get to Boise Idaho give me a call.
e. Dan tried every trick in his bag but the ball wouldn't fall.
f. The big walleyes seem, to go for these bright yellow lures, but the crappies just take jigs.
g. The town, where I grew up was quiet but the people weren't.
h. When he came home, my father brought a souvenir from Seoul Korea where he was stationed and one from Honolulu, Hawaii where he stopped on the way back.
i. For people who don't drink this can be a serious problem.
j. Carol had wanted many things, in her life, but she couldn't remember wanting anything, quite as much as this exciting challenging job.
k. Often we'd lie awake far into the night telling jokes and swapping stories about friends we'd known back home.
1. Last summer Larry bought a light blue RX 7 which he totaled a week later.