The number one billion has different values depending on where you are in the world and is based on different number naming systems. The long and short scales are two of several different large-number naming systems used throughout the world for integer powers of ten. Many countries, including most in continental Europe, use the long scale whereas most English-speaking countries use the short scale. In all such countries, the number names are translated into the local language, but retain a name similarity due to shared etymology. Some languages, particularly in East Asia, have large number naming systems that are different from the long and short scales.
Long scale refers to a system of large-number names in which every new term greater than million is 1,000,000 times the previous term: billion means a million millions (1012), trillion means a million billions (1018), and so on.
Short scale refers to a system of large-number names in which every new term greater than million is 1,000 times the previous term: billion means a thousand millions (109), trillion means a thousand billions (1012), and so on.
For most of the 19th and 20th centuries, the United Kingdom uniformly used the long scale, while the USA a used the short scale, so that usage of the two systems was often referred to as British and American respectively. In 1974, the government of the UK switched to the short scale, a change that is reflected in its mass media and official usage. Although some residual usage of the long scale continues in the UK, the phrases British usage and American usage are no longer accurate characterisations.