American and British English are very similar. There are, however, a few differences of grammar, vocabulary and usage. The following guide is meant to point out the principal differences between American and British English.

Differences in usage

Abbreviations

We usually write abbreviations without full stops in modern British English. Full stops (US periods) are normal in American English.

Mr (US Mr.) = Mister

Dr (US Dr.) = Doctor

Ltd (US Ltd.) = Limited (company)

Kg (US kg.) = kilogram

All and all of

Before a noun with a determiner (e.g. the, this, my), all and all of are both possible in British English. American English usually has all of.

She has eaten all (of) the cake. (GB)

She has eaten all of the cake. (US)

All (of) my friends like riding. (GB)

All of my friends like riding. (US)

Expressions with prepositions and particles

Different from/than (US)

Different from/to (GB)

Check something (out) (US)

Check something (GB)

Do something over/again (US)

Do something again (GB)

Live on X street (US)

Live in X street (GB)

On a team (US)

In a team (GB)

Monday through/to Friday (US)

Monday to Friday (GB)

Informal use of like

In an informal style, like is often used instead of as if/though, especially in American English. This is not considered correct in a formal style.

It seems like it is going to rain.

He sat there smiling like it was his birthday.

On

In American English, it is common to leave out on before the days of the week.

I am seeing her Sunday morning. (US)

British people say at the weekend; Americans say on the weekend.

What did you do at the weekend? (GB)

What did you do on the weekend? (US)

In and for

In American English, in can be used, like for, to talk about periods up to the present. (British English only for).

I havent seen her in years. (US)

Both and both of

Before a noun with a determiner (e.g. the, this, my), both and both of are both possible in British English. In American English, both of is usual.

Both (of) my parents like riding. (GB)

Both of my parents like riding. (US)

In after negatives and superlatives

After negatives and superlatives, in can be used to talk about duration. This is especially common in American English.

I havent seen him for/in months.

It was the worst storm for/in ten years.

In British English, in is not normally used with this meaning.

I havent seen him for months. (GB)

Shant

In British English, I shant is sometimes used in refusals. This is very unusual in American English.

I dont care what you say, I wont/ shant do it. (GB)

I dont care what you say, I wont do it. (US)

Shall

Questions with shall I/we are used (especially in British English) to ask for instructions or decisions, to offer services and to make suggestions. This is not common in American English.

Shall I open the window?

Shall we go out for a meal?

Will

We often use will in threats and promises. Shall is also possible in British English, especially after I and we. In American English, shall is not used in threats and promises.

I will/shall give you a teddy bear for your birthday. (GB)

I will give you a teddy bear for your birthday. (US)

Have (got) + infinitive

Have (got) + infinitive can be used, like must, to express certainty. This is mainly an American English structure, but it is now becoming more common in British English.

I dont believe you. You have (got) to be joking. (= You must be joking.)

Would and should

After I and we, should can be used in British English with the same meaning as would.

If we had a map we would/should be able to get out of here. (GB)

If we had a map we would we able to get out of here. (US)

Conditional would is sometimes used in both clauses of an if-sentence. This is common in spoken American English.

It would be better if they would tell everybody in advance.

A complete guide to the differences between American and British English can be found at http://www.perfectyourenglish.com/writing/english-writing.htm.