American and British English differences

American English in its written form is standardized across the U.S. (and in schools abroad specializing in American English). Though not devoid of regional variations, particularly in pronunciation and vernacular vocabulary, American speech is somewhat uniform throughout the country, largely because of the influence of mass communication and geographical and social mobility in the United States. After the American Civil War, the settlement of the western territories by migrants from the east led to dialect mixing and levelling, so that regional dialects are most strongly differentiated in the eastern part of the country that were settled earlier. The General American accent and dialect (sometimes called 'Standard Midwestern'), often used by newscasters, are traditionally regarded as the unofficial standard for American English.

British English has a reasonable degree of uniformity in its formal written form. On the other hand, the forms of spoken English – dialects, accents and vocabulary – used across the British Isles vary considerably more than in any other English-speaking areas of the world, and more so than in the United States, because of a much longer history of dialect development in the English speaking areas of Great Britain and Ireland. Dialects and accents vary, not only between England, Northern Ireland, Scotland and Wales (which constitute the United Kingdom), and the Republic of Ireland, but also within these individual countries. There are also differences in the English spoken by different socio-economic groups in any particular region. Received Pronunciation (RP) (also referred to as BBC English or the Queen's English) has traditionally been regarded as 'proper English' – 'the educated spoken English of south-east England'. The BBC and other broadcasters now intentionally use a mix of presenters with a variety of British accents and dialects, and the concept of 'proper English' is now far less prevalent.

British and American English are the reference norms for English as spoken, written, and taught in the rest of the world; for instance, the English-speaking members of the Commonwealth of Nations often (if not usually) closely follow British orthography, and many new Americanisms quickly become familiar outside of the United States. Although the dialects of English used in the former British Empire are often, to various extents, fairly close to standard British English, most of the countries concerned have developed their own unique dialects, particularly with respect to pronunciation, idioms, and vocabulary; chief among them are, at least for number of first-language speakers, Australian English and Canadian English.