About two-thirds of the world's population is bilingual, yet, according to this novel encyclopedia, the phenomenon of bilingualism is still to be properly analysed and defined. Bilingualism is complex because an individual's proficiency in a particular language may vary depending on whether we are referring to his or her skills in speaking, understanding, reading or writing.

Bilinguals often use language for different functions and purposes at different times. Up to a certain point in my life, living in India, I only read English but did not speak or write it; at that time English was an additional language that enabled me to gain entry into western ideas and thoughts. Later, living in England, the opportunities to speak and write English gave scope for me to develop as a true bilingual.

But does having two languages throw one's thought processes into disarray, creating identity crises or conflicts of cultural loyalty? Can language be a determining factor in defining ethnicity? Does acquired knowledge and skills in the so-called dominant languages such as English or French subtly undermine subaltern languages?

Since the late 1940s we have been inhabiting an increasingly interdependent world. This is true of both material and of conceptual commodities: look at the huge success of microwavable balti dishes in our supermarkets and the novel, The God of Small Things , in our bookshops. Yet, curiously, most of us have barely begun to notice, let alone comprehend, the core issues underlying our linguistic diversity.

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In everyday life in Britain, multilingualism as an expression of multiculturalism is confined to signs in some public places that are often inappropriate, erroneous and condescending, such as notices written in Bengali and Hindi displayed upside down. This does not help to create the positive atmosphere to which the host society is supposedly committed. Such attitudes to a language are important as a barometer of its perceived importance. The prestige of a language is closely associated with the economic and political power of those who are its native speakers. The considerable interest in learning Japanese and Russian testifies to that; and the prestige of English is why so many Americans remain monolingual.

In Britain, we have a poor track record in learning foreign languages. Even the present national curriculum is biased, conservative and short-sighted with regard to the learning of additional languages. As a result it is difficult to find suitably qualified language teachers, especially outside the European languages. But Britain is still perhaps the only country in which a genuine empathy between races and cultures has been forged in literature, music, the visual arts and human relationships. Admittedly, there is some amount of deep-rooted institutional as well as personal prejudice, but there is still a sound body of decent, sane people who "think clearly, feel nobly and act rightly" (in the words of a Nobel prize-winning bilingual Rabindranath Tagore).

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This encyclopaedia is one outcome of such an outlook. The editors state in their preface: "This encyclopaedia seeks to raise awareness about language diversity, to help reduce the prejudice and stereotyping that surround language minorities and to communicate the beauty of bilingualism." It will enhance understanding of this sensitive subject in an informed, unbiased and constructive way.

Certainly, it is the most comprehensive reference book on bilingualism yet published. Divided into four sections and covering 118 topics ranging from bilingualism in the family to bilingualism in the world, the writing is clear, concise and comprehensible, with multiple attractive text boxes and photographs of real situations and people. Although there are no cumbersome footnotes, further reading lists are given at the end of each topic. There is also a bibliography consisting of more than 2,000 entries.

However, too many examples and references come from the Welsh bilingual context with which the editors are clearly intimately familiar. Perhaps this is excusable, given the passions excited by the Welsh-English bilingual issue. Also, the section on loan words does not mention Hobson-Jobson , the well-known pioneering glossary of Anglo-Indian words and phrases (bungalow, juggernaut, khaki etc), first published in 1886, which celebrates the linguistic enrichment that came out of colonial India.

The most interesting section, in my view, is "Languages in Society". Running to about 250 pages, it raises important questions about dialects versus languages, bilingualism and language boundaries, bilingualism and the internet, language battles in the European Union, and so on. The discussion of languages in conflict is full of fascinating facts, graphic in layout, and handy for quick reference.

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At this point it is worth asking whether bilingualism could be a temporary trend? Can it survive the increasing penetration of English via the information superhighway? Are we not becoming more and more mono-lingual in the wake of the worldwide spread of the Anglo-American ethos? Are minority languages endangered and in need of policies for protection? Is not English the only language through which a Japanese businessman can have a meaningful communication with an Indian importer? Is separate language tuition confusing small children by asking them to read in writing systems using different orientations, as is the case with Urdu and Chinese? Is cultural and linguistic pluralism productive at one level but inhibiting at the level of really significant artistic achievement? These and many other questions kept arising as I picked my way through this volume, which is beautifully sewn, so that it remains faithfully open while the reader ponders.

The Encyclopedia of Bilingualism and Bilingual Education is a stimulating, enriching and necessary resource for professional linguists and educationists, and will surely prove of great interest to others too.

Krishna Dutta is an education consultant advising the London Borough of Haringey.