Many users twist around one tongue

Specialising in women and other diseases" is how a Rome clinic advertises itself. And a Turkish dentist: "Teeth extracted by latest methodists." Such droll examples of fractured English are collected to fill whole books, and their humour lies in their intelligibility. But what of "Trap step of refuge", the sign on an emergency staircase in a Japanese hotel? Here the severity of the fracture defeats understanding and could lead to disaster - no funny matter.

The fragmentation of English into hundreds of varieties is the subject of Tom McArthur's excellent book. As founding editor for 15 years of the journal English Today he is well placed to collect material on such variation. Vastly more people worldwide speak some form of English as their second, third or fourth language than the total number of those for whom it is their mother tongue. Maintaining international intelligibility among speakers who think they are using English is a big problem, as air crashes have graphically shown.

A hundred years ago an Oxford linguist predicted that the two main varieties (British and American) would soon become mutually unintelligible, and a similar warning was repeated by another Oxford linguist recently. Until the arrival of globalised communications and the internet, such predictions had some credibility.

Yet another Oxford linguist continues to claim that there is no "standard English" anyway, while simultaneously promoting the irreconcilable view that standard English (which, as every schoolchild knows, evolved in the 15th century) was indeed invented in 19th-century England by a group of middle-class intellectuals.

McArthur has a beautifully documented chapter, which will be much cited, on the emergence of the concept of standard English. The idea of standardness is, of course, crucial to the way all these rich varieties are regarded, by both speakers and hearers. He makes a strong claim that every variety should be regarded as legitimate in its own sphere - standard and non-standard forms "on the same level".

The difficulty, which he grapples with but never completely surmounts, is that prestige is conferred on language varieties by being institutionalised in education systems, which in turn presupposes codification. Only a tiny proportion of these hundreds of varieties of English have had their grammatical usages codified and their vocabularies collected in dictionaries. Even then to become what McArthur calls an "alternative prestige model" they must be identified with a set of functions that carries as high a level of respect as perceived "educatedness" in such societies - indeed in most societies.

Throughout southern Africa, for example, there is a rich mosaic of forms of English, all of which have an identifiable flavour of Africanness. Scholars such as N. Ndebele, until recently a vice-chancellor in the region, have argued for the recognition of a distinctively southern African English whose speakers and writers would not be marked down in exams for their "incorrect" usages. In the early 1990s a university in Japan, advertising for teachers of English, specified that speakers of Caribbean or Indian English would be particularly welcome.

The same commendable catholicity of approach underlies McArthur's book, but the problem lies in the reception that graduates of such institutions have in gaining acceptance - among employers and others - for the variety of English in which they have taken pains to graduate. Taken, indeed, many extra pains, since the texts are simply not available, certainly with sufficient coverage, in the varieties concerned. The most desirable outcome is that students would become able to use, in acceptable ways, both standard English and the regional variety. From McArthur's illuminating chapter on "Ebonics in the USA", a similar point emerges.

As a Scot, the author offers plenty on the multiplicity of Scottish Englishes, and, alongside the efforts by the late Peter Strevens, the Kashmiri-American Braj Kashru and the German Manfred Gorlach, he offers his own attempt to depict diagrammatically the potentially complex relationship between the older and newer Englishes.

All this has an important point: that we cease to think always of English as a single entity. But it is also possible to lose sight of the equally important point: that there is a sense in which it is still essentially true that there is one English - that there is still more unity than there is diversity, and that nearly all these varieties (with a few that McArthur suggests are doubtful) have more in common than the sum total of their differences, and that it is access to one of the mainstream models of English that will do most to empower learners.

Granted that reservation, we can welcome the likelihood that McArthur's sober celebration of that great diversity is set to become a classic in its field.

John Honey is professor of English-language education, University of Botswana.