1,000 * 1,000,000 = 1,000,000,000 = 10^9 = 1 giga-

Thus, a US billion has 9 zeroes.

This is called a ''Milliarde'' in German, where Germans mean a EuropeanBillion by the word ''Billion''.

The UK spelling of the old name is milliard (contrast with the German spelling). The series then continues with billion (tera, US trillion), billiard (peta, US quadrillion, source of the name of a pool-oid table ball-game), trillion and presumably trilliard (not Trillian ;^)

The BBC World Service uses the term ''thousand million'' so that everyone will understand what is being referred to.

However, these names, though still current in Europe, are archaic in England (and possibly also in the more civilized countries of Britain). Rupert Murdoch ''[an ex-Aussie - Australia was AFAIK the second country to take up the AmericanBillion]'' uses the US terms, so his vassals do, too.

As I understand it, the US usage changed when journalists had exhausted the wow-value of blabbing on about millionaires and a few of that nation's most wealthy came to have control over a milliard of dollars; the journalists, it seems, either did not understand what a billion was, or found the word ''milliardaire'' inadequately sensational. AnyOldWhichWay, they ended up referring to these giga-dollar plutocrats as billionaires; and, as they say, TheRestIsHistory.

* Just curious...any references for that?  I've often wondered why "billion" means different things in different places.  The above seems somewhat plausible; OTOH it seems to depend on some rather unflattering stereotypes of Yanks that are often trafficked... 

** Dr. Evil (sticking finger aside mouth):  "One.... MILLION.... Dollars!!!!!!!"
** UN Assembly: <burts out laughing>

''So when they say "there are 100 Billion stars in the MilkyWay" is that 100*10^9 or 100*10^12? How do astonomers talk about magnitudes the world over?'' to each other 4*10^11 +/- 2*10^11 stars (always give errors), to general public this would probably be translated to 400 bllion or 400 thousand million or 400 milliarde etc. depending on audience
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See also BritishBillion