Dilp Mukerjea writes in his new book, BrainTales:

The Emergence of English as The World’s Premier Language

The history of the English language commenced with the arrival of three Germanic tribes, the Angles, the Saxons, and the Jutes, into Britannia. They crossed the North Sea from what today is Denmark, and northern Germany, around A.D. 449. At that time the inhabitants of Britain spoke a Celtic language. The invaders spoke a Low Germanic tongue that, in its new setting, became Anglo-Saxon, or Old English, the ancestor of the English we use today. It was not long before these Teutonic plunderers pushed the Celtic speakers west and north into what is now Wales, Scotland and Ireland. The Angles were the dominant tribe; during the reign of King Egbert in the ninth century, the land became known as Englaland (“the land of the Angles”) and the language Englisc—from which the words England and English are derived. 

A major influence on the English language took place with the next conquest of England, two centuries after the rule of Egbert, by the Norman French, who came from Normandy. These people had been Vikings and freebooters from the Scandinavian countries. They spoke French and had taken to French customs. The invasion took place in 1066, under William, Duke of Normandy. In a bloody battle at Hastings, the Normans defeated the Saxons and Danes, and killed Saxon King Harold. They forced the surviving nobles to accept Duke William as King of England. 

Now, one may wonder why French did not become the language of England. Victory by the French-speaking Normans resulted in them far outnumbering their captives. This meant that, in order to communicate with them, they needed to learn English. In time, they lost their ties to France, and took to English as easily as their Norman forbears had dropped their Norse speech for French. Old English morphed into Middle English because many French words entered the vocabulary. 

Meanwhile, with the Roman conquest of England in the first century B.C. by Julius Caesar, many Latin words had crept into and stayed within the English language. This was further bolstered with the influence of the Roman church and missionaries a few centuries later. Thus, by the time the Normans were well settled in England, the influence of Latin, either directly or indirectly, was permanent. 

During the Renaissance, from the fourteenth to the seventeenth century, Europe witnessed the rediscovery of a love affair with all things Latin and Greek. Many classical words entered the English vocabulary, mainly via scholarly writing, and due to new discoveries in art, science, medicine, literature, and world geography. 

Whilst Anglo-Saxon is the foundation of the English language, its linguistic evolution resulted in a mingled history and a three-tiered vocabulary: Anglo-Saxon, French, and Latin / Greek. This means, in essence, we now have three options for conveying approximately the same meaning. The main difference between Early Modern English and Late Modern English is vocabulary. 

The much larger vocabulary of Late Modern English is due to two principal factors: new words arising from the Industrial Revolution and its associated technology; secondly, the British Empire at its height covered one quarter of the earth’s surface, and the English language adopted foreign words from many countries. 

Some expressions that the British call “Americanisms” are in fact original British expressions that were preserved in the colonies while lost for a time in Britain (for example trash for rubbish, loan as a verb instead of lend, and fall for autumn; another example, frame-up, was re-imported into Britain through Hollywood gangster movies). Spanish also had an influence on American English (and subsequently British English), with words like canyon, ranch, stampede and vigilante being examples of Spanish words that entered English through the settlement of the American West. French words (through Louisiana) and West African words (through the slave trade) also influenced American English (and so, to an extent, British English). 

Today, American English is particularly influential. This is due to the American dominance of cinema, television, popular music, trade and technology (including the Internet). But there are many other varieties of English around the world, including for example, Australian English, New Zealand English, Canadian English, South African English, Indian English and Caribbean English. The essential reasons for the ascendancy of English lie in the internationality of its words and the relative simplicity of its grammar and syntax.

During the Renaissance, from the fourteenth to the seventeenth century, Europe witnessed the rediscovery of a love affair with all things Latin and Greek. Many classical words entered the English vocabulary, mainly via scholarly writing, and due to new discoveries in art, science, medicine, literature, and world geography. Whilst Anglo-Saxon is the foundation of the English language, its linguistic evolution resulted in a mingled history and a three-tiered vocabulary: Anglo-Saxon, French, and Latin / Greek. This means, in essence, we now have three options for conveying approximately the same meaning. 

The main difference between Early Modern English and Late Modern English is vocabulary. The much larger vocabulary of Late Modern English is due to two principal factors: new words arising from the Industrial Revolution and its associated technology; secondly, the British Empire at its height covered one quarter of the earth’s surface, and the English language adopted foreign words from many countries. 

Some expressions that the British call “Americanisms” are in fact original British expressions that were preserved in the colonies while lost for a time in Britain (for example trash for rubbish, loan as a verb instead of lend, and fall for autumn; another example, frame-up, was re-imported into Britain through Hollywood gangster movies). Spanish also had an influence on American English (and subsequently British English), with words like canyon, ranch, stampede and vigilante being examples of Spanish words that entered English through the settlement of the American West. French words (through Louisiana) and West African words (through the slave trade) also influenced American English (and so, to an extent, British English). 

Today, American English is particularly influential. This is due to the American dominance of cinema, television, popular music, trade and technology (including the Internet). But there are many other varieties of English around the world, including for example Australian English, New Zealand English, Canadian English, South African English, Indian English and Caribbean English. The essential reasons for the ascendancy of English lie in the internationality of its words and the relative simplicity of its grammar and syntax.