[This is a fast-access FAQ excerpt.]
by Ken Moore, assisted by Olivier Bettens
The U.S. and traditional British names for large numbers are as
U.S. Traditional British
10^6 million million
10^9 billion thousand million or milliard
10^12 trillion billion
10^15 quadrillion thousand billion
10^18 quintillion trillion
10^21 sextillion thousand trillion
10^24 septillion quadrillion
10^27 octillion thousand quadrillion
10^30 nonillion quintillion
10^33 decillion thousand quintillion
10^36 undecillion sextillion
10^39 duodecillion thousand sextillion
10^42 tredecillion septillion
10^45 quattuordecillion thousand septillion
10^48 quindecillion octillion
10^51 sexdecillion thousand octillion
10^54 septendecillion nonillion
10^57 octodecillion thousand nonillion
10^60 novemdecillion decillion
10^63 vigintillion thousand decillion
The word "billion" has existed in France since the 15th century.
Opinions differ as to its initial meaning: one possibility is that
it meant 10^12 to mathematicians and 10^9 to others. The first
use in England recorded in the OED is by Locke in 1690: the
quotation clearly shows that for Locke it meant 10^12. This
remained the standard British meaning until the middle of the 20th
century. Early in the 18th century, French arithmeticians revised
its meaning to 10^9, and the U.S., acquiring the word directly from
the French, took this meaning also.
French has the word "milliard", also meaning 10^9, which had
largely displaced "billion" by the beginning of the 20th century.
("Milliard" is given in English dictionaries, though most of the few
people who know it would think of it as a French word.) By 1948,
the use of large numbers in the sciences and the declining value of
the franc led the French Weights and Measures conference to
recommend the return of "billion" to its original meaning of 10^12.
This became official policy in 1961. For more information on
international usage, see
By this time, the British had been introduced to the U.S.
meaning. MEU warns us that the usages differ; MEU2 (1965) suggests:
"Since billion in our sense is useless except to astronomers, it
is a pity that we do not conform [to the U.S. meaning]". The
British Government took this advice in 1974, when Prime Minister
Harold Wilson announced to the House of Commons that the meaning
of "billion" in papers concerning Government statistics would
thenceforth be 10^9, in conformity with U.S. usage.
Despite this, the U.S. meaning is still rare outside journalism
and finance, its introduction having served merely to create
confusion. Throughout the U.K., a common response to the question
"What do you understand by 'a billion'?" would be: "Well, I mean a
million million, but I often don't know what other people mean."
Few schoolchildren are confident of the meaning, though, again,
10^12 seems to be preferred. Many well-educated adults, aware of
both meanings, either avoid the term altogether or use it only in
the unambiguous phrases "English billion" and "American billion".
English-speaking South Africans, Australians, and New Zealanders
are similarly reluctant to use a term that has become ambiguous.
Scientists have long preferred to express numbers in figures
rather than in words, so it is easy to avoid "billion" in contexts
where precision is required. The plural is still used freely with
the colloquial meaning of "a very large number".
OED, Editions 1 and 2.
Robert, Dictionnaire historique de la langue francaise.
P Pamart, "A propos d'une reforme des mesures legales", in "Vie et
Langage", (125)1962, pp 435-437.