It's important to know the rules of English punctuation when you write, as using the wrong punctuation may lead to misunderstandings. Using the correct punctuation is especially important when you are writing to impress, such as when you are applying for a new job, or when you are writing to a customer.

Here is a guide to the rules for using the more common punctuation marks in English.

When to use capital letters

1. At the beginning of the sentence

It's cold today.

2. For the personal pronoun "I"

I live in a big city.

3. For "proper nouns"

- names and titles: Sarah, Mr Stevens, Doctor Roberts
- places and countries: London, England,
- nationalities and languages: He is French, She speaks Italian
- companies, products and brands: Microsoft, Coca Cola
- institutions: The Ashmolean Museum, The Department of Trade
- religions and religious festivals: Christianity, Ramadan
- abbreviated names: The BBC

4. For books, television and radio programmes, newspapers and magazines

The Simpsons, The Times.

5. Days of the week and months of the year

Wednesday, August 10th.

6. Historical periods or events

The Russian Revolution

7. Rivers, mountains and lakes and geographical regions

The Amazon, The Middle East

8. In addresses

Flat 2, 16 London Road.

When to use commas in English

1. To separate items in a list

We need coffee, tea, sugar and milk.

British English writers do not normally put a comma before "and", although in American
English, a comma can be used.

"We need coffee, tea, sugar, and milk."

2. To separate clauses which are related in meaning

Do you know the answer, or should I ask Tony?

Where the clauses are short, commas are not used:

"I was tired so I went home."

3. After introductory phrases

Unfortunately, I cannot send you the information.

4. Before and after a word or phrase that interrupts the main clause

Some children,if they are gifted, attend special schools.

5. Before and after non-defining clauses

The factory workers, who were in a meeting, decided to accept the pay offer.
= All the factory workers were in a meeting.

Compare with a defining clause (which restricts the noun).

The factory workers who were in a meeting decided to accept the pay offer.
= Only the factory workers who were in a meeting decided to accept the offer: those workers who were not in the meeting didn't decide to accept the offer.

6. To show millions, thousands and hundreds

5, 890, 2811
10, 050

When to use a full stop

(or "period" in American English)

1. At the end of the sentence

Thank you for your letter.

2. After initials in American English

Mr. G. Hoover. (The British English version is "Mr G Hoover")

3. As a decimal point

2.5%, $9.99.

When to use a colon

1. To introduce a list

You will need to bring the following: a waterproof jacket, a change of clothes, a battery-operated torch and some matches.

2. To introduce explanations

There is one thing to remember: the nights can get cold, so bring a warm jacket.

3. To write the time
The 10:40 train to London is late.

4. Between the title and subtitle of a book

Shakespeare: The Complete Works

When to use a semi-colon in English

Semi-colons show a pause which is longer than a comma, but not as long as a full stop. Short clauses which are related in meaning can be separated by a comma. However, if the clauses are longer, you will probably need a semi-colon:

We'll need to hold some meetings abroad with our suppliers; please could you check your availability in April.

1. To separate long items in a list

Our writing course includes several components: correspondence, including
letters and emails; style and vocabulary choice; punctuation; layout and planning.

2. To give balance to sentences, or to link parallel sentences

We went out for the day; they stayed in.

When to use an apostrophe in English

1. With an s to show possession

The company's profits.

The 's comes after singular nouns and after irregular plural nouns (those which do not end in s).

The company's staff, the children's shoes.

But the apostrophe follows the swhen the noun is plural and regular.

Compare:

The boy's school (school of one boy) and the boys' school (school of many boys.)

With nouns which end in y in the singular, but end in ies in the plural (like company) the apostrophe follows the s when it is plural.

The company's profits (profits of one company) and the companies' profits (profits of more than one company.)

With hyphenated nouns, the 's comes at the end of the word.

My brother-in-law's Ferrarì.

2. To show abbreviation

I don't like smoking. (= do not)

3. In time references

In two weeks' time.

Be careful!

1. Apostrophes are not used for possessive pronouns.

Whose is this pen? (Not "Who's this pen" as "who's" = who is.

That pen is hers. (Not "That pen is her's.")

Its also exists as a possessive pronoun:

Its market has grown. (The market of the company).
(Not "It's market" as "it's" = it is or it has.)

2. Apostrophes are not used to make a plural of nouns that end in a vowel.

For example, "two memos" (not "two memo's").