American english or British english?

This article outlines the differences between American English, the form of the English language spoken in the United States, and Commonwealth English (often called British English).
For the purposes of this article:
American English is the form of English used by people in the United States and, as a lingua franca or second language, by people in many parts of the world. American English does not include Canadian English; although Canadian pronunciation and vocabulary is very similar to that of the United States, Canadian spelling often takes the Commonwealth form. Regions and countries that tend to use American English in teaching and publishing include much of Eastern Europe (including Russia), the Far East (especially Japan, South Korea, Taiwan, and the Philippines; although largely excluding the former British colonies of Hong Kong and Singapore), the Americas (excluding other former British colonies such as Canada, Jamaica, and the Bahamas) and, in Africa, Liberia, and Namibia. The World Bank, and the Organization of American States, among other organizations, also use American English. Commonwealth English is the form of English used across the United Kingdom and most of its former colonies in the British Empire, most notably in much of Africa (including South Africa and Egypt), the Indian subcontinent (Pakistan, India, and Bangladesh), Malta, Australia and New Zealand, and portions of Southeast Asia (Myanmar, Singapore, Malaysia and Thailand), as well as Hong Kong. Like American English, it is used in many parts of the world as a lingua franca. This form of English, mostly interchangeable with British English, is sometimes called Commonwealth English because most of its speakers live in nations that are members of the Commonwealth of Nations. Other nations and groups to use British English include the European Union and, often, the United Nations. Many international organizations, like the International Olympic Committee, NATO, the World Trade Organization and ISO also use British English. The forms of English spoken in Canada exhibit features of both British and American dialects; though spelling is closer to British English, pronunciation and vocabulary are much closer to American English. Many words and phrases thought of as "Americanisms" are also used by Canadians. Although British English is a term used when describing formal written English used in the United Kingdom, the forms of spoken English used in the United Kingdom vary considerably more than in most other areas of the world in which English is spoken, even far more than in the United States, despite the vastly larger population and land area of the U.S. Dialects and accents vary not only within regions of the UK—for example, in Scotland, Northern Ireland, and Wales—but also within England, with differences occurring within the space of a few miles in some cases. The written form of the language as taught in schools is universally Commonwealth English with a slight emphasis on a few words which might be more common in the specific areas than others. For example, although the words "wee" and "small" are interchangable, one is more likely to see "wee" written by a Scot than by a Londoner. Although spoken American and British English are generally mutually intelligible, there are enough differences to occasionally cause awkward misunderstandings or even a complete failure to communicate. George Bernard Shaw once said that the United States and United Kingdom are "two countries divided by a common language"; a similar comment is ascribed to Winston Churchill. Henry Sweet predicted in 1877 that within a century, American English, Australian English and British English would be mutually unintelligible, but it may be the case that increased world-wide communication through radio, television, the Internet, and globalization has reduced the tendency to regional variation. This can result either in some variations becoming extinct (as, for instance, truck has been gradually replacing lorry in much of the world) or in the acceptance of wide variations as "perfectly good English" everywhere.
In addition to its use in English-speaking countries, English plays an important role as a technical language around the world, in medicine, computer science, air traffic control, and many other areas of concentrated expertise and formal communication among international professionals.