I will give more information about the American system, and present the
French system and the Japanese system.
The American system
The American naming convention is the following:
103(n+1) shall be spelled
(n)illion, where (n) is a Latin root for
See the write-up by Alias for the examples.
The French system
Webster 1913 is outdated about billion and trillion. Nowadays, the
French system is the same as the English system, i.e. 1 billion =
1000 milliards = 1012. The naming convention is the following:
106n shall be spelled (n)illion.
Examples: 1012 = 1 billion, 1018 = 1 trillion,
1024 = 1 quatrillion, and so on.
This rule was enunciated in an appendix of the government decree
61-501 of May 3rd, 1961.
However, common usage says "quadrillion" instead of "quatrillion",
and adds intermediate numbers: 1 billiard = 1000 billions, 1 trilliard
= 1000 trillions, and so on.
The Japanese system
Not only large numbers have distinct names in Japanese, but they also
have distinct characters (kanji), so that you need to learn each of them
separately. I will give the pronunciations only.
The basic unit is not 103, but 104. For example,
you don't say "3 million yens" in Japanese, but something like "300
tenthousands yens". The numbers are:
See Japanese numbers and counting for more details. gn0sis tells me that they borrowed this system from the Chinese. See Chinese numbers.