A billion is, by definition, a million to the second power - that is, 1 000 000 000 000. Unfortunately we seem to have adopted the illiterate and innumerate American system whereby a billion is a million to the one-and-a-halfth power, a trillion a million to the second power, a quadrillion a million to the two-and-a-halfth power, and so absurdly on.
The correct term for a thousand million is a milliard. Why don't we use it?
Yes, chakka is spot on. Its unfortunate that so may measures (even count in this case) have been sucessfully distorted over the years, but these days a billion can be assumed to mean 1,000,000,000.
I wonder if many serious mistakes have been made over this in the past? If I quote a company �1 billion to fulfil a contract and claim it meant �1,000,000,000,000 could I get away with it?!
Good question pagey, but surely in the contract there would be the amount in digits as well as words. and what contract would be worth 1 billion pounds?
I don't think that anyone uses the British billion 'in public' these days. What I mean is that, while some people might still use it when they're chatting in the pub or talking to their great aunt Agatha, all 'official' sources now use the American definition. So, when the BBC refer to the government allocating a billion pounds to a project, they only mean 9 zeros. (This is despite the fact that the statement has come from a British organisation and refers to British currency).
MarkyP05 - getting a bit off topic, but we deal with (US) billion dollar contracts all of the time - you only need to buy/sell/float a moderately large company for contracts to hit billions. But any lawyer worth even half their salt would define this in the form of the full number as well (and usually it's not in round billions, so they would state it in millions).