British English (BrE) is the form of English used in the United Kingdom. It includes all English dialects used in the United Kingdom.

American English (AmE) is the form of English used in the United States. It includes all English dialects used in the United States.

Written forms of British and American English as found in newspapers and textbooks vary little in their essential features, with only occasional noticeable differences in comparable media (comparing American newspapers with British newspapers, for example). This kind of formal English, particularly written English, is often called "standard English".

The spoken forms of British English vary considerably, reflecting a long history of dialect development amid isolated populations. In the United Kingdom, dialects, word use and accents vary not only between England, Northern Ireland, Scotland and Wales, but also within them. Received Pronunciation (RP) refers to a way of pronouncing standard English that is actually used by about two percent of the UK population. It remains the accent upon which dictionary pronunciation guides are based, and for teaching English as a foreign language. It is referred to colloquially as "the Queen's English", "Oxford English" and "BBC English", although by no means do all graduates of the university speak with such an accent and the BBC no longer requires it or uses it exclusively. The present monarch uses a hyperlect of the Queen's English.

An unofficial standard for spoken American English has also developed, as a result of mass media and geographic and social mobility, and broadly describes the English typically heard from network newscasters, commonly referred to as non-regional diction, although local newscasters tend toward more parochial forms of speech. Despite this unofficial standard, regional variations of American English have not only persisted but have actually intensified, according to linguist William Labov.[citation needed]

Regional dialects in the United States typically reflect some elements of the language of the main immigrant groups in any particular region of the country, especially in terms of pronunciation and vernacular vocabulary. Scholars have mapped at least four major regional variations of spoken American English: Northern, Southern, Midland, and Western. 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 parts of the country that were settled earlier. Localized dialects also exist with quite distinct variations, such as in Southern Appalachia, Boston and the New York City area.

British and American English are the reference norms for English as spoken, written, and taught in the rest of the world, excluding countries where English is spoken natively such as Australia, Canada, Ireland and New Zealand. In many former British Empire countries where English is not spoken natively, British English forms are closely followed, alongside numerous AmE usages which have become widespread throughout the Anglosphere. Conversely, in many countries historically influenced by the United States where English is not spoken natively, American English forms are closely followed. Many of these countries, while retaining strong BrE or AmE influences, have developed their own unique dialects, which include Indian English and Philippine English.

Chief among other native English dialects are Canadian English and Australian English, which rank third and fourth in the number of native speakers. For the most part, Canadian English, while featuring numerous British forms alongside indigenous Canadianisms, shares vocabulary, phonology and syntax with American English, leading many to recognize North American English as an organic grouping of dialects. Australian English likewise shares many American and British English usages alongside plentiful features unique to Australia, and retains a significantly higher degree of distinctiveness from both the larger varieties than does Canadian English. South African English, New Zealand English and the Hiberno-English of Ireland are also distinctive and rank fifth, sixth and seventh in the number of native speakers.