Use a question mark at the end of a direct question.
Who left the door open?
Are you ready to leave yet?
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Do not use a question mark at the end of an indirect question, which is a question inside of a statement. An indirect question is a part of a statement, so use a period.
Comma
We use commas with words, phrases, or clauses that come in a series. Use commas:
With three or more items in a series joined by and or or. Use a comma when a sentence contains a series of items (nouns, phrases, or clauses) joined by and.
He served broccoli, mashed potatoes, and carrots with dinner.
They went to the mall, shopped for new clothes, and went to the movies.
Alison vacuumed the living room, Tim washed the dishes, Diane cleaned the bathroom, and Liz shouted instructions to all of them.
The last comma in the series (before and) is optional.
He served broccoli, mashed potatoes and carrots with dinner.
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Avoid excess commas with items in a series. Do not use a comma:
With only two items in a series
Before the first item in a series
After the last item in a series
After and or or
With such as. Such as can be used to introduce an example or examples. Use a comma before such as.
This summer, I want to learn to cook Italian food, such as lasagna, spaghetti, and linguine.
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Do not use a comma after such as.
Between two or more adjectives in a series. Use a comma between two or more coordinate adjectives in a series. (Coordinate adjectives can have their order changed and can be joined with and.)
He bought some ugly red T-shirts. (You cannot say “red ugly T-shirts,” so a comma is not needed.)
The intelligent, hardworking students got high grades. (You can say “hardworking, intelligent,”
so a comma is needed.)
Between two independent clauses in a sentence. Use a comma when two independent clauses are joined into a single sentence with and, but, or, nor, for, yet, or so. An independent clause has a complete subject and verb and can stand alone as a sentence.
My dog likes to go outside, and my cat likes to sleep in front of the fireplace.
He went to the supermarket, but he forgot to buy milk.
The mechanic will fix the problem, or I will have to buy a new car.
She was locked out of her apartment, for she lost her keys on the bus.
He spent the whole day at the water park, yet he never got wet.
They didn’t check a map before leaving, so they got lost almost right away.
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Do not join two independent clauses with only a comma. This error is often called a “comma splice.”
Franklin cut the lawn in the morning, his brother cleaned the garage.
Correct a comma splice by joining the clauses with a semicolon or with a comma and and,
but, or, nor, for, yet, or so.
Franklin cut the lawn in the morning, and his brother cleaned the garage.
Franklin cut the lawn in the morning; his brother cleaned the garage.
A comma is not needed when the clauses are very short.
She got up and he made breakfast.
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Do not use a comma to join only two compound elements, such as compound subjects or predicates, or compound objects of prepositions. Compound elements are joined with words such as and, but, and or.
Between a dependent clause and an independent clause. Use a comma to join a dependent clause followed by an independent clause. A clause has a complete subject and a complete verb.
An independent clause can stand alone. A dependent clause cannot stand alone as a sentence. A subordinating conjunction (such as when, if, though, while, etc.) joins the two clauses.
If I win the grand prize in the lottery, I’ll buy a new house and a new car.
Though she wasn’t hungry, Mavis ate a slice of pizza.
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Do not use a comma to join an independent clause followed by a dependent clause.
Other subordinating conjunctions include so that, that, and in order that.
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Do not confuse so with so that. So introduces an independent clause. A comma is needed before so.
So that means “in order that” and introduces a dependent clause. A comma is not needed before so that, because a comma is not needed when an independent clause is followed by a dependent clause.
A comma is needed when the clause with so that begins the sentence.
Before and after an appositive. An appositive is a noun or noun phrase that uses other words to restate the noun just before it. Commas always come before and after an appositive.
George Washington, the first president of the United States, was elected in 1789.
I’d like to introduce my uncle, Don Mantle. He owns a used bicycle shop, Don’s Bikes.
For more information on appositives, see page 56.
After an introductory prepositional phrase. A prepositional phrase is formed with a
preposition and a noun. Prepositional phrases can modify nouns, verbs, or a whole sentence. An introductory prepositional phrase is at the beginning of a sentence and modifies the whole
sentence. Use a comma after an introductory prepositional phrase, unless the phrase is very short.
At the beginning of the winter driving season, motorists should check their radiator fluid.
In summer check your coolant, (no comma necessary)
For more information on prepositions and prepositional phrases, see page 238.
After an introductory participial phrase. A present participle is a verb + -ing. A past participle is a verb + -ed. Participles are used with forms of be or have to form various tenses.
Participles can also be used as modifiers. An introductory participial phrase is formed with a present or past participle and its objects and modifiers. An introductory participial phrase is followed by a comma.
Quickly running downstairs, Dale tripped and fell down.
Bored by the long speeches, Laura and Julie dozed off.
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A comma is not needed after but or although when one of these words begins a sentence.
After an introductory adverb. When an adverb begins a sentence and modifies the whole sentence, it is set off with a comma.
Exceptionally, employees may be granted time off if they make up the time.
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Do not use a comma after an adverb at the beginning of the sentence if it modifies only one part of the sentence, such as an adjective that follows it.
Before and after an interrupting phrase. Use commas before and after a word or phrase that interrupts a sentence.
John wants to go to Florida on vacation. Mary, however, wants to go to California.
Before and after words in direct address. Use commas before and after a word that is said in direct address (i.e., said directly to the listener).
Lucy, what did you do to your hair?
I think, Dale, that your suggestion is a good one.
Let’s go, everybody!
In dates. Use a comma between the day and the year in dates.
Today is April 13, 2009.
The United States declared independence from Britain on July 4, 1776.
In locations. Use a comma before and after the state when both city and state appear together.
The Declaration of Independence was signed in Philadelphia, Pennsylvania.
Washington, DC, is the capital of the United States.
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Avoid unnecessary commas. Do not use a comma between:
The subject and the verb
A preposition and its object
An adjective and the noun it modifies
Colon
Use a colon after an independent clause to introduce a list.
This box contains your new computer equipment: a keyboard, a monitor, a printer, and a mouse.
Trace needs these ingredients to make banana bread: bananas, flour, oil, sugar, salt, and baking powder.
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Do not use a colon to separate a verb and its objects.
Use a colon after an independent clause to introduce an idea.
After wandering for hours, they could reach only one conclusion: they were lost.
I have a great suggestion: let’s go to the beach on Sunday.
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Do not use a colon between a preposition and its object or objects.
For more information on prepositions, see page 238.
Semicolon
Use a semicolon to link independent clauses without a coordinating conjunction.
Margo graduated from college; however, she decided to travel for a year before getting a job.
Some people deny that global warming is a problem; most scientists disagree with them.
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Do not use a semicolon in place of a colon.