The English language was first introduced to the Americas by British colonization, beginning in the late 16th and early 17th centuries. Similarly, the language spread to numerous other parts of the world as a result of British trade and colonization elsewhere and the spread of the former British Empire, which, by 1921, held sway over a population of 470–570 million people, approximately a quarter of the world's population at that time.
Over the past 400 years, the form of the language used in the Americas—especially in the United States—and that used in the United Kingdom have diverged in a few minor ways, leading to the versions now occasionally referred to as American English and British English. Differences between the two include pronunciation, grammar, vocabulary (lexis), spelling, punctuation, idioms, and formatting of dates and numbers, although the differences in written and most spoken grammar structure tend to be much less than those of other aspects of the language in terms of mutual intelligibility. A small number of words have completely different meanings in the two versions or are even unknown or not used in one of the versions. One particular contribution towards formalizing these differences came from Noah Webster, who wrote the first American dictionary (published 1828) with the intention of showing that people in the United States spoke a different dialect from Britain, much like a regional accent.
This divergence between American English and British English has provided opportunities for humorous comment, e.g., George Bernard Shaw has a character say that the United States and United Kingdom are "two countries divided by a common language"; and Oscar Wilde that "We have really everything in common with America nowadays, except, of course, the language" (The Canterville Ghost, 1888). Henry Sweet incorrectly predicted in 1877 that within a century American English, Australian English and British English would be mutually unintelligible (A Handbook of Phonetics). It may be the case that increased worldwide communication through radio, television, the Internet and globalization has reduced the tendency towards regional variation. This can result either in some variations becoming extinct (for instance, the wireless, being progressively superseded by the radio) or in the acceptance of wide variations as "perfectly good English" everywhere.
Although spoken American and British English are generally mutually intelligible, there are occasional differences which might cause embarrassment—for example, in American English a rubber is usually interpreted as a condom rather than an eraser; and a British fanny refers to the female pubic area, while the American fanny refers to an ass (US) or an arse (UK)....LESS