Understanding How to Punctuate
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Understanding How to Punctuate
What the punctuation marks mean
Period
Comma
Nothing (no punctuation mark)
Semicolon
Colon
Here are some warnings about the colon
Here are effective uses of the colon
Here are ineffective uses of the colon
Minor Errors
Clauses
An independent clause can be a sentence
A dependent clause is a fragment
Concluding advice about punctuation and sentence structure
Do not use an entire sentence to state the subject of the sentence that you should have written in the first place
If you take two sentences to tell one thought or one incident, you must use the period
When a positive sentence follows a negative sentence, do not give in to the temptation to use a comma. Use a period
Re-write short, choppy sentences or at least use periods
Some complete sentences sound incomplete.
Pronouns can be subjects of sentences
A command is a complete sentence
Do not let pointers trick you into under-punctuating
Two complete sentences in dialogue must have a period between them
Extra comments starting with “which” create fragments needing a comma
Extra comments starting with “this” create sentences needing a period
Notice whether a subject is re-stated in the word group after a coordinating conjunction
When “so” means “thus” (or “therefore”), put a comma in front
When “so” means “in order that,” do not put a comma in front
What the punctuation marks mean
Period
A period tells the reader, “That was one complete sentence, and here comes another.”
Sometimes the two sentences are short:
Jim is generous. He loaned me his car.
Sometimes the two sentences are disguised with pointers (NOT CONJUNCTIONS) in front:
Also, I need money. Therefore, I took a second job.
Sometimes unexplained pronouns are the subjects:
It puzzles me. They seemed so harmless.
Sometimes one sentence is a command:
Take my word for it. Football is tough.
An extra period creates a fragment. A missing period results in a splice or run-on. These three errors are penalized more severely than any other punctuation errors.
Substitutes for the period include:
(a) a comma plus a coordinating conjunction:
I wanted to go, but my car was in the shop.
(b) a semicolon with or without a pointer:
Sue waited an hour; then she went home.
Jim isn’t simply big; he is a giant.
I warned him twice; nevertheless, he persists in cutting class.
Comma
A comma tells the reader, “One of the word groups–either the one to the left or the one to the right–cannot stand alone as a sentence.”
Rule 1: Put a comma after a leading fragment:
(a) After leaving the room, she listened at the door.
(b) If you do not believe me, you could look it up.
Rule 2: Put a comma before a closing fragment not starting with a conjunction or a preposition:
(a) Then he handed her the flowers, a wilted handful of carnations bought at a roadside stand.
(b) Although she sunburns easily, she does not like to wear a hat, especially on a windy day.
Rule 3: A comma and a coordinating conjunction together can join a complete sentence to another complete sentence:
(a) Al worked all day on his car, but he could not fix it.
(b) On the tenth day of the tenth month, Jim bet ten dollars on horse number ten, and it finished tenth.
Commas have many other uses, such as separating items in a series, setting off words, and in dates.
Nothing (no punctuation mark)
Sometimes the correct punctuation is to put nothing:
Rule 1: Put nothing if a closing fragment begins with a subordinating conjunction:
(a) Wendy gets mad whenever she loses at tennis.
(b) Jo got an A on the exam although she did not even study for it.
Rule 2: Put nothing if a closing fragment is joined with a coordinating conjunction:
(a) She called her parents and told them not to wait up for her.
(b) I want to go to the mall but not with all your friends.
Rule 3: Do not stick a comma between a subject and its verb:
X (a) The best way to study, is to start with your most difficult subjects.
X (b) The runner with the best chance of winning, should be the one from Kenya.
Rule 4: Do not stick a comma between a verb and the words that it connects to the subject:
X (a) The problem with that concrete is, too much sand in the mix.
X (b) The result of all her hard work was, a promotion with a twenty percent pay raise.
Semicolon
The semicolon and the period are the same choice. Both show two complete sentences. Use the semicolon when the second complete sentence explains or completes or comments on the thought in the first complete sentence.
This clause ends with a semicolon; this punctuation mark shows a complete sentence in front of it and after it.
Thus a semicolon is pretty much the same as a period; both show two complete sentences and no conjunctions.
There are slight technical differences between a period and a semicolon; semicolons do not need capital letters after them; also semicolons have only one space after them; periods have two.
Do not overuse semicolons; save them for closely-related sentences; for example, this page uses far too many semicolons.
Colon
This sentence uses a handy punctuation mark: the colon. The colon has one purpose: it tells readers that what they expect is coming.
Anything can follow a semicolon: a list, one word, a fragment, or even a complete sentence–with or without a capital letter.
Here are some warnings about the colon
a. Do not use it with words like “such as” or “for example.” The colon means: “such as” or “for example.”
b. Use the colon only after a complete sentence that sets up an expectation. For example the red colon above is wrong.
c. Do not overuse colons. Save them for emphasis. This page uses far too many colons.
Here are effective uses of the colon
1. Sue looks for one quality in men: money.
2. Dating Jim has one big drawback: he does not have a car.
3. Her vegetarian diet is strict: no red meat, no chicken, no fish, no dairy products.
4. In the 1990’s the American military suffered an embarrassing irony: Its Commander-in-Chief was a draft dodger.
5. Al’s Halloween costume was offensive: a used Pampers.
Here are ineffective uses of the colon
1. Yesterday I met Jim: he does not have a car.
(The first sentence does not set up an expectation.)
2. Her vegetarian diet is strict, such as: no red meat, no chicken, no fish, no dairy products.
(The colon means “such as”–no need to repeat.)
3. Al’s Halloween costume was: a used Pampers.
(A complete sentence should come before the colon. The unnecessary colon cannot set up an expectation or emphasis on its own.)
Minor Errors
Punctuation errors that do not involve the period are minor. A minor error may coast you one point in a paper, whereas each comma splice, run-on, or fragment may cost you 5-10 points. Here are some examples of minor errors:
(a) The comma is right, but the choice was nothing:
X 1. Whenever my child is lying he bites his lower lip.
X 2. Jim missed the highway exit which took him two hours out of his way.
X 3. Al bought himself a sports car but he bought his wife a pickup truck.
(b) Nothing is right, but the choice was comma:
X 1. My daughter bites her lip, whenever she is lying.
X 2. Al bought his wife a pickup truck, and told her to start up a lawn care business.
One minor error involves the period:
X 1. Al bought himself a sports car. But he bought his wife a pickup truck.
Here the period does not really cause a fragment, but something is wrong because “but” is a conjunction that is supposed to keep us in the same sentence.
Professional writers sometimes begin sentences with “but” or “and” when they want to achieve an informal tone. However, you should be careful of making that choice.
Clauses
A clause is a group of words with a subject and a complete verb. (A group of words without a subject or a complete verb is called a phrase.)
Is a clause a sentence? Maybe, maybe not.
An independent clause can be a sentence:
Jim’s father is a cop.
It is in the bedroom.
A dependent clause is a fragment:
X Although Jim’s father is a cop,
X If it is in the bedroom,
X The dress that Sue wore to the dance.
Concluding advice about punctuation and sentence structure
Do not use an entire sentence to state the subject of the sentence that you should have written in the first place:
Next comes my sister Alice. She is a real monster.
Then there was the electric bill. This was $540.
You cannot force these into one sentence by using a comma. Use the period or revise them.
My sister Alice is a monster.
The electric bill was $540.
If you take two sentences to tell one thought or one incident, you must use the period:
Network televsion is full of junk. I stopped watching it.
My parents will not take a cruise. They both get seasick.
I met your boyfriend in a bar last night. He hit on me.
When a positive sentence follows a negative sentence, do not give in to the temptation to use a comma. Use a period:
Hurricane Andrew was not a problem. It was a disaster.
Successful insurance agents don’t want your approval. They want your money.
We didn’t just win. We killed them.
It’s not for me. It’s for my mother.
Re-write short, choppy sentences or at least use periods.
Some writers are weak. They do not combine information in one sentence. They write two sentences. They write more than two sentences. Their sentences are short. They sound choppy. This clue gives examples. These sentences are short. They are choppy. Weak writers try to disguise short sentences. They put commas between them. This creates comma splices. Splices are bad.
Some complete sentences sound incomplete.
Most complete sentences sound complete. This one doesn’t. The full meaning of “This one doesn’t” is implied:
“This complete sentence does not sound complete.”
“This one doesn’t” is a complete sentence, even though it leaves out what seem to be important words, including the last half of the verb: “sound.” Many students do not understand this concept. You should. (meaning “You should understand this concept”).
Pronouns can be subjects of sentences, even if the reader does not know what the pronouns stand for:
It is broken.
They left.
She knows about it.
That was wrong.
He put it there.
It begins tomorrow.
They want it.
A command is a complete sentence. The understood subject is “you”:
Do your homework.
Consider rap music. It is full of violence.
Take college, for example. It is expensive.
Do yourself a favor. Don’t take drugs.
Don’t risk getting AIDS. Use safe sex.
Take my advice. Enjoy your youth.
Don’t buy a Cavalier. Mine was a piece of junk.
Do not let pointers trick you into under-punctuating.
Be sure to block out pointers. It is almost as though these words were invented to trick you into using commas where you need periods:
First he called. Then he wrote a letter.
He did not pay his fees. Thus he was dropped from every class roll.
Next they repossessed my truck. Now I really have problems.
Also, I must go to the bank. Otherwise, my checks will bounce.
Two complete sentences in dialogue must have a period between them:
Then my dad said, “You wrecked my Mercedes. I’m grounding you for three years.”
Then he lied and said, “I can’t come to the bachelor party. My wife is sick.”
My roommate said, “I can’t loan you any money. I’m broke.”
Extra comments starting with “which” create fragments needing a comma:
He paid over $15,000, which was too much.
Extra comments starting with “this” create sentences needing a period:
He paid over $15,000, this was too much.
(This structure is informal, but if you use it, at least punctuate it properly.)
Notice whether a subject is re-stated in the word group after a coordinating conjunction:
My dog is fun but causes a great deal of trouble.
My dog is fun, but he causes a great deal of trouble.
When “so” means “thus” (or “therefore”), put a comma in front
Sue did not answer her phone, so I drove to her house.
When “so” means “in order that,” do not put a comma in front:
Sue called to remind him so that he would not miss the meeting.
Sue called to remind him so he would not miss the meeting.
Last updated 9/18/06