# Better names needed for large numbers

## The word ‘centibillionaire’ is a linguistic travesty

One year ago, there were just two centibillionaires, Jeff Bezos and Bill Gates. Recently, Facebook's Mark Zuckerberg has joined the Amazon and Microsoft founders. Elon Musk, chief executive of Tesla and SpaceX, is tipped to be next to join this exclusive club.

The word ‘centibillionaire’ has slithered into common usage for someone with a net worth of more than \$100 billion. The term is a linguistic travesty: the prefix ‘centi’ normally connotes one hundredth part of something, as when it precedes metre or gram.

So, a centibillion is suggestive of one hundredth of a billion, or 10 million. Alas, the misuse is probably irreversible.

The problem arises from the paucity of terms in common language for large numbers. In our decimal system, the magnitude of numbers increases by a factor of 10 for each additional digit; there should be a unique name for each power of 10 up to 20 or so.

We are indebted to ancient Indian mathematicians for the development of the decimal number system. These mathematicians were fascinated by large numbers, and had names for powers of 10 far beyond anything in common use today. Bhaskara, who flourished in the seventh century, was the first mathematician to write numbers using a circle for the zero. This zero – this “nothing” – gives the number system enormous power and versatility.

#### Shortcoming

Bhaskar, a mathematically gifted seven-year-old named after the ancient savant, was a character in Vikram Seth’s blockbusting novel A Suitable Boy, a story recently adapted for television. Speaking to Haresh, a love interest of Lata, the main character, Bhaskar points out a shortcoming in our counting system: names are lacking for some of the powers of 10. “First you have 10, that is, 10 to the first power. Then you have a hundred, which is 10 times 10, which makes it 10 to the second power. Then you have a thousand, which is 10 to the third power. But for the next power, 10,000 or 10 to the fourth power, there is no special word.”

The fifth, sixth and seventh powers of 10 – one followed by five, six and seven zeros – are a lakh, a million and a crore. Two of these names, popular in India, are also familiar to crossword solvers. The eighth power of 10, 100 million, has no particular name, the ninth power is a billion, and the tenth power is again anonymous. Bhaskar concludes that "it's amazing that we don't have a word in either English or Hindi for a number that is as important as 10 to the tenth".

Haresh recalls that Chinese merchants use 10,000 as a natural measuring point “just as we use a lakh”. He consults a Chinese colleague in Kanpur and learns that the missing terms are wan (to rhyme with ‘kaan’) and ee (to rhyme with ‘knee’).

“This gives, in order of powers of 10: one, ten, hundred, thousand, wan, lakh, million, crore, ee, billion.” For 10 to its own power Haresh found no special word, and wrote to Bhaskar: “You will have to invent one for yourself. I suggest bhask.”

Here is a challenge for inventive readers of The Irish Times: devise a number-naming system that is lucid, unambiguous and aesthetically pleasing and that will rid us of the dog’s dinner that is a centibillion.

Peter Lynch is emeritus professor at UCD School of Mathematics and Statistics. He blogs at: thatsmaths.com