Q: WE talk of millions, billions and trillions. What comes next? - W Sewell, Bishop Auckland.

A: A MILLION is a single word for a thousand-thousand and is numerically written as 1,000,000. The numerical definition of a billion, in Britain at least, is not quite so clear. In America a billion is 1,000,000,000 - a thousand million, or ten to the power of nine. Traditionally, this figure was known in Britain as a milliard.

In Britain, a billion was traditionally 1,000,000,000,000 - a million-million, or ten to the power of 12, the twelve representing the number of zeros. This is what the Americans call a trillion, but in Britain a trillion was a higher value (ten to the power of 18) and every named value above this figure had a different meaning in the two nations. There is some argument over whether we should use the British or American system, although both originated in France.

The term billion was first recorded in France in the 15th Century, where it seems mathematicians used it to define the figure of ten to the power of 12, and all others defined it as ten to the power of nine. The first of these definitions was widely adopted in Britain and was standard by the 17th Century. Strangely, the French mathematicians abandoned it in the 1700s in favour of ten to the power of nine, in what came to be known as the American system.

Meanwhile, a need for international recognition made the American definitions more widespread and, by the mid-20th Century, Britain was showing preference for the American billion. A significant political event in Britain was the official adoption of the American definition by Harold Wilson's government in 1974.

Numerically, millions, billions and trillions are followed by quadrillions, quintillions, sextillions, septillions, octillions, nonillions, decillions, undecillions, dodecillions, tredecillions and on so on. Again, the actual definitions for these vary between American and traditional British. It can be seen that elements like 'bi' and 'tri' have numerical significance. This means that there is no such thing as a zillion, as is often thought.

I believe that the largest officially defined number is a centillion, ten to the power of 3003. However, there is one defined number that breaks away from the -illion pattern of suffixes. This is the googol, or ten to the power of 100. This number is also known as ten dotrigintillion in America, or ten thousand sexdecillion in the old British system.

Published: Monday, March 11, 2002

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