English is the medium of instruction at my eight-year-old daughter's school in Mumbai. She is also taught French. She can speak Hindi (which has the fraught and controversial status of being India's national language) as well as a smattering of Marathi (the language that is native to Maharashtra, the western Indian state of which Mumbai is the capital) and is fluent in Bengali (our mother tongue).

At home, we speak Bengali. But while we do that, we unconsciously use English words in every other sentence. These words (whether "please", "thanks" or "sorry", or more complex, loaded ones) have become so intimately braided into the fabric of the Bengali language that we no longer think of them as "English words", nor do we ever use their Bengali equivalents. I don't know whether my daughter thinks in English, but I notice that
whenever she feels the urge to express something strongly, she switches almost entirely to English.

So it comes as a sort of vindication to learn towards the end of Robert McCrum's erudite, riveting and often very funny Globish that "about half the world's population - approximately four billion people - have knowledge of, or acquaintance with" English.

McCrum does not use the term "Globish", coined by Jean-Paul Nerrière, a French-speaking former IBM executive and amateur linguist, in its original sense. Nerrière was talking about a sort of "decaffeinated English", unencumbered by the rules of grammar and shorn of its rich vocabulary, stripped down to a core set of words that are a means to a single end: comprehensible cross-cultural communication. McCrum deals with the world's English as it is written and spoken across the planet, and explores how and why it came to be such an inextricable part of global consciousness. Globish, he tells us in his prologue, is the biography of this phenomenon.

It is a huge undertaking, and if the biography on occasion teeters on the edge of being a hagiography, that is very much to do with the nature of the subject. McCrum alludes to, but does not go very deep into, the divisive function of English in post-colonial societies, in which it is the instinctive language of the educated middle class and, like French and Latin once upon a time in England, is the language in which so many of those societies conduct their intellectual discourse.

Rather, his interest - and it is a fascinating subject to be interested in - lies in the manner in which English, born in "a foggy archipelago off the north-west coast of Europe", has transcended the legacy of empire and of Anglo-American supremacy to become "a supra-national means of global communication".

The chicken-and-egg question that McCrum tries to answer is this: has globalisation engendered this phenomenon, or does global capitalism feed off the chameleon-like, enduring nature of the English language? The author goes on an astute and intrepid search that brings together old-fashioned pavement-pounding reporting, scholarly consideration of theory, and a keen sense of the language and its canonical practitioners.

One of the chief reasons for English becoming the world's language is its history, its flexibility and its ability to embrace influences. That is how it is suitable for high and low culture, as much for the formal as for the demotic. You can rear (English) or raise (Norse) a child, McCrum tells us at one point. Later, he quotes Keats on Shakespeare's "negative capability" (an annihilation of the self that allows the poet's mind to be "a thoroughfare for all thoughts") and draws a parallel with the English language.

Globish - "contagious, adaptable, populist and subversive" - mirrors English in this respect. Drawing on an enormous range of influences that grows exponentially in a world in which 175,000 blogs are born every day, and fired by the ambition to inhabit a global village, Globish is not merely flourishing, but at times seems on the verge of leaving English behind and becoming a different tongue.

“Globish remains based on trade, advertising and the global market," McCrum writes in his epilogue in answer to the question he set himself at the beginning. "With its supranational momentum, above and beyond American and British influence, Globish sustains itself as both chicken and egg."

A perfect Globish moment occurred on the eve of the football World Cup in South Africa. Match officials were given a list of swear words in English and asked to watch out for them. One of the linesmen said: "We can't do this in 11 different languages, but at least we have to know the swear words in English." Yes, that's right, that will do very nicely, thank you. McCrum should have been delighted.

Globish: How the English Language Became the World's Language
Robert McCrum
Viking, 320pp, £20

Soumya Bhattacharya edits the Mumbai edition of the Hindustan Times, one of India's foremost English-language dailies, and is the author of the novel "If I Could Tell You" (Tranquebar Press)