English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria. Following the economic, political, military, scientific, cultural, and colonial influence of Great Britain and the United Kingdom from the 18th century, via the British Empire, and of the United States since the mid-20th century, it has been widely dispersed around the world, become the leading language of international discourse, and has acquired use as lingua franca in many regions. It is widely learned as a second language and used as an official language of the European Union and many Commonwealth countries, as well as in many world organizations. It is the third most natively spoken language in the world, after Mandarin Chinese and Spanish.

Historically, English originated from the fusion of languages and dialects, now collectively termed Old English, which were brought to the eastern coast of Great Britain by Germanic (Anglo-Saxon) settlers by the 5th century – with the word English being derived from the name of the Angles. A significant number of English words are constructed based on roots from Latin, because Latin in some form was the lingua franca of the Christian Church and of European intellectual life. The language was further influenced by the Old Norse language with Viking invasions in the 8th and 9th centuries.

The Norman conquest of England in the 11th century gave rise to heavy borrowings from Norman-French, and vocabulary and spelling conventions began to give the superficial appearance of a close relationship with Romance languages to what had now become Middle English. The Great Vowel Shift that began in the south of England in the 15th century is one of the historical events that mark the emergence of Modern English from Middle English.

Owing to the significant assimilation of various European languages throughout history, modern English contains a very large vocabulary. The Oxford English Dictionary lists over 250,000 distinct words, not including many technical or slang terms, or words that belong to multiple word classes.