Note: This page or section contains IPA phonetic symbols in Unicode. See IPA chart for English for a pronunciation key.
Modern English is English spoken since the great vowel shift, completed in roughly 1550.
Despite some differences in vocabulary, material from the early 17th century, such as the works of William Shakespeare and the King James Bible, is considered to be in Modern English, or more specifically, they are referred to as Early Modern English, and most people who are fluent in the English of the early 21st century can read these books with little difficulty.
Modern English has a large number of dialects, spoken in diverse countries throughout the world. Most of these, however, are mutually intelligible. This includes American English, Australian English, British English, Canadian English, Caribbean English, Hiberno-English, Indo-Pakistani English, New Zealand English, Singaporean English and South African English. These dialects may be met in different contexts, for example some American actors in Hollywood historical or mythic epics often employ British-derivative accents while many British, Australian and non-native English-speaking international pop singers sing in an 'industry neutral' American accent to appeal to an international demographic.
According to Ethnologue, there are over 508 million speakers of English as a first or second language as of 1999, a number dwarfed only by the Chinese language in terms of the number of speakers. However, Chinese has a smaller geographical range: it is spoken primarily in mainland China and Taiwan, and by a sizable immigrant community in North America. In contrast, English is spoken in a vast number of territories, including Great Britain, Ireland, Canada, the United States of America, Australia, New Zealand, India, Pakistan and Southern Africa. Its large number of speakers, plus its worldwide presence, have made English a common language for use in such diverse applications as controlling airplanes, developing software, conducting international diplomacy, and business relations.

History
Early Modern English lacked uniformity in spelling, but Samuel Johnson's dictionary, published in 1755 in England, was influential in establishing a standard form of spelling. Noah Webster did the same in America, publishing his dictionary in 1828; see American and British English spelling differences.
Public education increased literacy, and more people had access to books (and therefore to a standard language) with the spread of public libraries in the 19th century. Many words entered English from other languages, as a result of contact with other cultures through trade and settlement, and the migration of large numbers of people to the United States from other countries. World War I and World War II threw together people from different backgrounds, and the greater social mobility afterwards helped to lessen the differences between social accents, at least in the UK. The development of radio broadcasting in the early 20th century familiarised the population with accents and vocabulary from outside their own localities, often for the first time, and this phenomenon continued with film and television.

Outline of changes in Modern English
See the sound changes c.1600-1725 and sound changes c.1725-1900 sections of the Phonological history of the English language page.

Syntax

History of the English Language
List of dialects of the English language
Old English
Middle English