According to the following extract from the ODO "billion" in BrE used to mean "a million million", but its meaning has changed to the more common AmE usage meaning "a thousand million".

  • In British English, a billion used to be equivalent to a million million (i.e. 1,000,000,000,000), while in American English it has always equated to a thousand million (i.e. 1,000,000,000). British English has now adopted the American figure, though, so that a billion equals a thousand million in both varieties of English.

The origin of this usage and its subsequent change, as explained by Etymonline, are from French:

  • 1680s, from French billion (originally byllion in Chuquet's unpublished "Le Triparty en la Science des Nombres," 1484; copied by De la Roche, 1520); see bi- "two" + million. A million million in Britain and Germany (numeration by groups of sixes), which was the original sense; subsequently altered in French to "a thousand million" (numeration by groups of threes) and picked up in that form in U.S., "due in part to French influence after the Revolutionary War" [David E. Smith, "History of Mathematics," 1925].

  • France then reverted to the original meaning in 1948. British usage is truer to the etymology, but U.S. sense is said to be increasingly common there in technical writing.

As far as I can remember (1980s), a billion, at least in finance, has always meant a thousand million, and I've never come across its older usage.


  • When did BrE adopted the AmE usage of a billion?

  • What was "a thousand million" called in BrE when a billion meant "a milliom million"?

  • The answer to part of your question is milliard. Can't help with the rest.
    – cobaltduck
    Nov 15, 2016 at 16:33
  • 2
    The last question is answered by "It was called a thousand million".
    – Andrew Leach
    Nov 15, 2016 at 17:08
  • It has happened in my lifetime which began during WW2. I started off thinking of a billion as a million million. @cobaltduck The French have stuck with milliard for what we now call billion, and their billion is what we call trillion. Must get confusing for people who number their wealth with more than nine noughts!
    – WS2
    Nov 15, 2016 at 17:22
  • @Andrew Leach - you are saying that it was not called "a milliard"?
    – user66974
    Nov 15, 2016 at 17:22
  • @JOSH Personally I don't recall the word milliard being used in English, though the OED has multiple examples of it: 1974 Encounter 43 iv. 58/2 English schoolchildren are still taught that a thousand million is a milliard.1990 Man 25 95 Milliards of deities assembled in front of the cave. I would guess that it was in the mid-seventies (effects of globalisation?) that in Britain we switched to the American billion. *
    – WS2
    Nov 15, 2016 at 17:27

3 Answers 3


Britain officially changed to the short scale system in 1974

source: http://hansard.millbanksystems.com/written_answers/1974/dec/20/billion-definition#S5CV0883P0_19741220_CWA_439

However, I would assume that the American usage had gained quite some popularity before this point otherwise its adoption wouldn't have been necessary.

The term you are looking for is milliard.

  • The American usage certainly had gained quite some popularity before that point. I clearly remember my father explaining the whole thing as soon as I was old enough to understand it, in about 1962 - so a dozen years before that point. Nov 27, 2016 at 23:30

I can't back this up, but I wonder if it is linked to increasing use of engineering notation and metric prefixis, which would make it more important to have a specific name for every multiple of a thousand. This would make "thousand million" undesirable, forcing a choice between adopting the American billion and the French milliard.




I was taught that a billion was a million million, but gave up on that years ago due to American usage. It's now a thousand million, or 10^9, or in old language, a milliard.

Usage of milliard would appear to have been declining since the 60s, as suggested by google ngrams:


As an academic writer I would say that there's no clear cut-off. Older people will continue to complain about incorrect usage; younger people will continue to adopt the newer terminology -- until the old people die.

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