Billion is a word for a large number with two distinct definitions:1,000,000,000, i.e. one thousand million, or 109, as defined on the short scale. This is now the most common sense of the word in all varieties of English; it has long been established in American English and has since become common in Britain and other English-speaking countries as well. 1,000,000,000,000, i.e. one million million, or 1012, as defined on the long scale. This number is the historical sense of the word and remains the established sense of the word in other European languages. Though displaced by the short scale definition relatively early in US English, it remained the most common sense of the word in Britain until the 1950s and still remains in occasional use there.