Punctuation
Correct punctuation will help your reader understand your writing; incorrect punctuation may make your writing difficult or impossible to understand. English punctuation (unlike English spelling and English grammar) is fairly simple and regular. Here are the most important rules of English punctuation.


A. At the beginning and end of a sentence (see The Sentence)
1. All sentences begin with a capital letter: A, B, C, D, E,….
(The other kind of letters are lower case: a, b, c, d, e,….)
2. All sentences end with a period or a question mark or an exclamation point: . ? !


B. The comma
1. A comma is used between items in a list when the list includes at least three items (see Parallel Structures):
I bought a book, a compact disk, and a videotape.
George, Fred, and Mary went shopping.
He got up, he took a shower, he ate breakfast, and he left the house.
Note that a coordinating conjunction comes before the last item. The comma before the conjunction is optional. Note also that the items can be words, phrases, or clauses and they must be parallel (see Parallel Structures).
2. A comma is used after a phrase or adverb clause (see Adverb Clauses) that comes before the subject of a sentence:
While I was cooking breakfast, the rest of the family was sleeping.
Before fixing an omelet, you must break some eggs.
Last night, I saw a really good movie.
If an introductory phrase is very short (2-3 words), the comma is optional:
Last night I saw a really good movie.
If an adverb clause comes after the main clause, the comma is not used:
The rest of the family was sleeping while I was cooking breakfast.
3. Commas separate extra (non-restrictive) words, phrases, or clauses from the rest of the sentence:
California, which is the most populous state, is in the western US.
California, the most populous state, is in the western US.
Also see Adjective Clauses.
4. A comma and a coordinating conjunction are used between two independent clauses (see Parallel Structures):
He watched TV, but she went to bed.
I went to the library, and I worked on my composition for several hours.
Our teacher says that English is easy, but the students don’t believe it.
The comma is optional when at least one of the clauses is short (5 words or less):
He watched TV but she went to bed.
5. A comma separates a quotation from the rest of the sentence:
The doctor said, “I will see you in the morning.”
“I will see you in the morning, ” the doctor said.
6. A comma separates a tag question from the rest of the sentence:
English is easy, isn’t it?
Billy didn’t know how to swim, did he?
They shoot horses, don’t they?


C. semicolon
1. A semicolon can be used between closely related independent clauses (see Parallel Structures):
English is easy; mathematics is difficult.
A semicolon is often used between independent clauses when the second clause includes a transition:
English is easy; however, mathematics is difficult.
2. A semicolon separates items in a list when at least one of the items contains a comma:
We visited San Francisco, California; Portland, Oregon; and Seattle, Washington.


D. The colon
1. A colon can introduce a list:
There are several things a student in a composition class needs to bring to every class meeting: paper, a pen, a dictionary, and the textbook.
2. A colon can introduce an explanation:
Some students are afraid to take composition classes: They think writing is too hard.


E. The apostrophe
1. An apostrophe indicates the place in a contraction where a letter or letters have been omitted:
is not = isn’ t
was not = wasn’ t
does not = doesn’ t
did not = didn’ t
she is = she’ s
they had = they’ d
2. An apostrophe indicates possession:
a. Add apostrophe + s to singular nouns and indefinite pronouns.
Fred’s car, my brother’s hat, somebody’s book
b. Add apostrophe only to plural nouns which end with -s.
the girls’ clothes, the teachers’ offices
c. Add apostrophe + s to plural nouns which don’t end with -s.
the children’s breakfast, the men’s tools


F. Dashes and parentheses
Dashes and parentheses separate extra information from the rest of the sentence. They are often used for explanations, examples, and comments. Material between the dashes and parentheses is not grammatically part of the sentence.
Most people born in the US speak only one language—English.
This device is easy