Is trillion the new billion?
The eurozone's bailout fund now stands at one trillion euros (£880bn or $1.4tn) after a deal was thrashed out in Brussels by European leaders. The figure of one trillion has become increasingly widely used but do we really understand it?
Once a representation of something beyond our comprehension, the word trillion - 1,000,000,000,000 - has now sealed its place in common parlance.
As US politicians were trying to find budget savings of $1.2tn, European leaders were topping up their rescue fund to the tune of 1tn euros.
A combination of economic progress and inflation means larger and larger numbers are needed to define financial sums, and a billion is no longer the benchmark. So how did trillion take over?
The words billion and trillion, or variations on them, were first documented by French mathematicians in the 15th Century.
A trillion was 1,000,000,000,000,000,000, or the third power of a million. The US later adopted what became known as the short scale, which reduced a trillion to 1,000,000,000,000 (and a billion to 1,000,000,000), but the British retained the old system until the 1970s.
At that point, the word trillion was rarely mentioned in the news and resided more in the imagination of children, alongside zillions and gazillions, as an expression of something on an enormous scale.
It was more commonly used in the US. The New York Times, for instance, anticipated the US economy in 1970 would soon surpass $1tn. But it only cropped up in the British media with regularity in the 1980s, in reference to the yen or the lira.
But the last few years has seen its increasing use and it has now supplanted a billion, says James Abdey, a fellow of statistics at London School of Economics.
"When it was first used in the 1970s it had shock value. The first time someone hears the word trillion, they might not know the number of zeros but they know it's a big number. But the figures are now bandied around in the media and it's devalued its importance."
The US is more used to the term, due to the size of its economy and its spending power.
"'Trillion' does seem to have much more currency than it used to, probably because of the costs of the Iraq and Afghanistan wars and the budget and deficit," says John Allen Paulos a professor of mathematics at Temple University in Philadelphia.
"This doesn't mean that most people have a visceral grasp of its size. It'd be interesting to have the presidential candidates asked during a debate, How many millions in a trillion? I suspect at least some of them would try to deflect the question with a joke. And emotion trumps the numbers as usual. A few million dollars spent on some hot-button issue often arouses more ire than a trillion-dollar war."
It's not only in the more affluent countries that the word has risen to prominence. Living in Zimbabwe during the height of its inflation problems in 2008, people became used to talking about their daily expenses in terms of trillions.
Elsewhere, economic growth has driven an inexorable rise in numbers, says economist Andrew Dilnot. "The speed of change you get from quite small annual growth is what catches us all out. If something is growing at 10% a year then it doubles every seven-and-a-quarter years."
But increased use has not enhanced understanding, he says. "My guess is that most people really struggle to have a clear idea of what a trillion is. I have to sit down and think pretty hard how many noughts there are.
"The answer I think is what we mean is 1,000 billion, which has 12 noughts. Some people still think a billion is a million-million, which is really a trillion, and they think a trillion is something else. So the honest answer is people just see a trillion and think it's a very, very big number."
If the area of a doormat is equal to one, the total area of the United Kingdom is a trillion times bigger - 1,000,000,000,000
- Doormat area: 0.24 sq m
- United Kingdom total land area: 244,820 sq km
About 20 years ago, a study suggested Italians were much more comfortable with big numbers than the British because of the lira, says Mr Dilnot, and despite the increased use of trillion in British discourse (most commonly about debt), the UK's national income is described as £1,500bn not £1.5tn, because the UK understands billions better.
One way to enhance understanding is to divide a big number by the number of people affected, he says, so if the population of the eurozone is about 330m, then a trillion shared represents about 3,000 euros for each person. Another way is to count the numbers one at a time, one per second. A million seconds is 11 days, a billion seconds is about 32 years and a trillion seconds is 32,000 years.
As well as the mathematical reality that numbers really are getting bigger, there is also a wilful repetition of words like trillion, says lexicographer Susie Dent.
"The use of 'trillions' in our general conversation is part of a trend towards linguistic inflation or 'bigging up'.
"Some words are used to the point of exhaustion and need replacing with others in order to maintain the strength of expression. So 'heroes' are now 'superheroes', we're not just angry any more, we are 'incandescent with rage', and 'tragedy' is losing its power because it's used for less than tragic events.
And words which previously had sufficient power in themselves are attracting prefixes such as uber- or mega- in order to re-energise them, she adds.
"'Trillion' has become a bit of a throw-away for a large amount."
Next up, quadrillion.