These two varieties of English are very similar that most American and British speakers can understand each other without great difficulty. There are, however, a few differences of grammar, vocabulary and spelling. The following guide is meant to point out the principal differences between American English (AE) and British English (BE).
Differences in Grammar
Use of the Present Perfect
The British use the present perfect to talk about a past action which has an effect on the present moment. In American English both simple past and present perfect are possible in such situations.
I have lost my pen. Can you borrow me yours? (BE)
I lost my pen. OR I have lost my pen. (AE)
He has gone home. (BE)
He went home. OR He has gone home. (AE)
Other differences include the use of already, just and yet. The British use the present perfect with these adverbs of indefinite time. In American English simple past and present perfect are both possible.
He has just gone home. (BE)
He just went home. OR He has just gone home. (AE)
I have already seen this movie. (BE)
I have already seen this movie. OR I already saw this movie. (AE)
She hasn't come yet. (BE)
She hasn't come yet. OR She didn't come yet. (AE)
The British normally use have got to show possession. In American English have (in the structure do you have) and have got are both possible.
Have you got a car? (BE)
Do you have a car? OR Have you got a car? (AE)
Use of the verb Get
In British English the past participle of get is got. In American English the past participle of get is gotten, except when have got means have.
He has got a prize. (BE)
He has gotten a prize. (AE)
I have got two sisters. (BE)
I have got two sisters. (=I have two sisters.)(AE)
In British English it is fairly common to use shall with the first person to talk about the future. Americans rarely use shall.
I shall/will never forget this favour. (BE)
I will never forget this favour. (AE)
In offers the British use shall. Americans use should.
Shall I help you with the homework? (BE)
Should I help you with the homework? (AE)
In British English needn't and don't need to are both possible. Americans normally use don't need to.
You needn't reserve seats. OR You don't need to reserve seats. (BE)
You don't need to reserve seats. (AE)
Use of the Subjunctive
In American English it is particularly common to use subjunctive after words like essential, vital, important, suggest, insist, demand, recommend, ask, advice etc. (Subjunctive is a special kind of present tense which has no -s in the third person singular. It is commonly used in that clauses after words which express the idea that something is important or desirable.) In British English the subjunctive is formal and unusual. British people normally use should + Infinitive or ordinary present and past tenses.
It is essential that every child get an opportunity to learn. (AE)
It is essential that every child gets an opportunity to learn. (BE)
It is important that he be told. (AE)
It is important that he should be told. (BE)
She suggested that I see a doctor. (AE)
She suggested that I should see a doctor. (BE)
She insisted that I go with her. (AE)
She insisted that I should go with her. (BE)
Collective nouns like jury, team, family, government etc., can take both singular and plural verbs in British English. In American English they normally take a singular verb.
The committee meets/meet tomorrow. (BE)
The committee meets tomorrow. (AE)
The team is/are going to lose. (BE)
The team is going to lose. (AE)
Auxiliary verb + do
In British English it is common to use do as a substitute verb after an auxiliary verb. Americans do not normally use do after an auxiliary verb.
May I have a look at your papers? You may (do) (BE)
You may. (AE)
'Have you finished your homework?' 'I have (done).' (BE)
'I have.' (AE)
As if/ like
In American English it is common to use like instead of as if/ as though. This is not correct in British English.
He talks as if he knew everything. (BE)
He talks like/as if he knew everything. (AE)
In American English it is also common to use were instead of was in unreal comparisons.
He talks as if he was rich. (BE)
He talks as if he were rich. (AE)
The indefinite pronoun One
Americans normally use he/she, him/her, his/her to refer back to one. In British English one is used throughout the sentence.
One must love one's country. (BE)
One must love his/her country. (AE)
Mid position adverbs
In American English mid position adverbs are placed before auxiliary verbs and other verbs. In British English they are placed after auxiliary verbs and before other verbs.
He has probably arrived now. (BE)
He probably has arrived now. (AE)
I am seldom late for work. (BE)
I seldom am late for work. (AE)