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Comma Errors

The most frequent errors in SSU student writing are comma mistakes. In fact, other researchers have found that comma mistakes are the most frequent errors in all writing. According to Chris Anson, Robert A. Schwegler, and Marcia F. Muth, “Of all the punctuation marks in English, the comma is probably the easiest to misuse” (The Longman Concise Companion 432). While many readers may not notice certain types of comma errors, comma errors can be distracting:

America's attention span, is zilch.

Most readers have been taught to pause when they reach a comma, so the comma between the subject and verb interrupts the flow of this sentence.

Although "pause at the comma" may be a a good rule for readers, it is not a good rule for writers. The rules for comma placement are very complicated. All grammar handbooks provide detailed instructions for comma use. If you are currently taking English 1101, 1102, or 1105, you should refer to Chapter 49 of The Longman Concise Companion (pages 426-37) when you have questions about using commas.

If you do not have a grammar handbook handy and you are looking for a quick "cheat sheet" for comma rules, the information below may help you. The following four comma "rules" are adapted from Sheridan Baker's The Practical Stylist, a book which attempts to provide simplified rules for grammar and punctuation while avoiding linguistic jargon.

Use commas to set off:

  1. INTRODUCERS,
  2. COORDINATORS,
  3. INSERTERS, and
  4. LINKERS.

Introducers

Examples

Unfortunately, he failed again. [The word Unfortunately introduces the sentence.]

Unfortunately for Herbert, the price went up the day before he bought his ticket. [The phrase Unfortunately for Herbert introduces the sentence.]

After the final, stop by my office and pick up your work. [The phrase After the final introduces the sentence.]

After the final stop, you must get off the train. [The phrase After the final stop introduces the sentence.]

At the beginning of June, we will take the trip. [The phrase At the beginning of June introduces the sentence.]

At the beginning of June and John’s wedding, the flower girl fled from the church. [The phrase At the beginning of June and John’s wedding introduces the sentence.]

Before you go, back the car out of the driveway. [The clause Before you go introduces the sentence.]

Before you go back, drop off the luggage. [The clause Before you go back introduces the sentence.]

Coordinators

Examples

He ran home, and he changed clothes before the meeting.
This and joins two “sentences” (independent clauses). The text would still be mechanically correct if the and were replaced with a period or a semicolon:

He ran home. He changed clothes before the meeting.
He ran home; he changed clothes before the meeting.

He ran home and changed clothes before the meeting.
This and does not join two “sentences.” The text would be incorrect if the and were replaced with a period or a semicolon:

He ran home. Changed clothes before the meeting.
He ran home; changed clothes before the meeting.

She was angry, but she kept her temper under control.
But joins two independent clauses:

She was angry. She kept her temper under control.

Fasten the panel with a screw, or it will come loose later.
Or joins two independent clauses:

Fasten the panel with a screw. It will come loose later.

Fasten the panel with a screw or nail.
Or joins two words:

Fasten the panel with a screw. Nail.

He loved her, for he recognized her inner beauty.
For joins two independent clauses:

He loved her. He recognized her inner beauty.

He loved her for one night.
For does not join two independent clauses:

He loved her. One night.

Remember, however, that you may need a comma before a coordinating conjunction to fulfill a separate comma rule. Sometimes, for example, you may need a comma before a coordinating conjunction--even one that introduces a word, phrase, or dependent clause--to help your readers understand your point. In some circumstances, a comma before but can alert your readers that a surprising contrast is coming. (See Linkers.)

Jane was angry but calm. [If your readers would expect Jane to remain calm, even when she is angry, there is no need for a comma.]
Jane was angry, but calm. [If your readers would expect Jane to behave like a raving lunatic when angry, you do want to add a comma.]

Inserters

May 2, 2008, will be the last day of the spring semester, but finals won’t end until May 9. [The 2008 clarifies the meaning of the sentence, but the core independent clause is May 2 will be the last day of the spring semester.]

Portsmouth, Ohio, has a floodwall covered with murals. [The Ohio clarifies that you are not writing about a city in New Hampshire, Iowa, Rhode Island, or Virginia. The core sentence is Portsmouth has a floodwall covered with murals.]

I know, however, that the movie started late. [The however helps readers process the text, but it does not change the meaning of the core sentence. When you have a transitional word like however in a sentence, try moving it around to see whether it should be set off with commas. In this case, However, I know that the movie started late and I know that the movie started late, however both work, too, so the commas are necessary. In contrast, in the sentence There’s no rush; take however long you need, the however is not set off by commas because however is in a fixed place in the sentence.]

Gordon is, by the way, next in line. [The core sentence is Gordon is next in line.]

My nephew, who is six, rides the bus to school. [If you are writing about only one nephew, this clause is extra information and should be enclosed in commas.]

My nephew who is six rides the bus to school. [If you are writing about two or more nephews, who is six is essential information: The only way readers will understand which specific nephew you are referring to in this sentence is if you include the clause.]

The software, which came with the computer, was useless. [If the only software you are writing about is that which came with the computer, which came with the computer is nonessential information that needs to be enclosed in commas.]

The software that came with the computer was useless. [If you are also writing about software that was purchased separately from the computer, that came with the computer is essential information and must not be enclosed in commas.

Important note: Who-clauses describe people. Some who-clauses contain essential information; some contain non--essential information. As a writer, it is your job to decide what type of information is in a who-clause in order to determine whether commas are necessary. Which-clauses and that-clauses describe things. Use a that-clause to provide essential information; do not surround a that-clause with commas. Use a which-clause to provide nonessential information; do surround a which-clause with commas.]

Linkers

She fell down the stairs, having twisted her ankle.

She fell down the stairs, broke her leg, and wound up in the hospital. [There are three items in a series here: (1) fell down the stairs, (2) broke her leg, (3) wound up in the hospital. If you had a pair—instead of a series—of items, you would not use a comma: She fell down the stairs and wound up in the hospital.]

She fell down the stairs, breaking her leg and wrenching her back.

She fell down the old, creaky, broken-down stairs.

She fell down the stairs because she twisted her ankle. [Because she twisted her ankle is a dependent clause that comes at the end of a sentence. Because of its position in the sentence, it is not separated from the independent clause with a comma.]

Because she twisted her ankle, she fell down the stairs. [Because she twisted her ankle is a dependent clause that comes at the beginning of a sentence. Because it is an introducer, it must be separated from the independent clause with a comma.]

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