Millions and more: Numbers larger than the millions can get problematic in both English and Spanish. Traditionally, a billion has been a thousand million in U.S. English but a million million in British English, and Spanish has followed the British standard, with a trillion being a thousand billions in either case.
Thus 1,000,000,000,000 would be a billion in British English but a trillion in U.S. English.
Precise Spanish, following the British understanding, uses mil millones for 1,000,000,000 and billón for 1,000,000,000,000, while trillón is 1,000,000,000,000,000. But U.S. English has influenced English outside the U.S. and Spanish as well, especially in Latin America, so there can be confusion both in Latin America and among English speakers outside the United States about exactly what a billion or billón is.
In Costa Rica a billion is referred to as mil millones.
One million (1,000,000) or one thousand thousand, is the natural number following 999,999 and preceding 1,000,001. The word is derived from the early Italian millione (milione in modern Italian), from mille, “thousand”, plus the augmentative suffix -one.
1,000,000,000 (one billion, short scale; one thousand million or milliard, long scale) is the natural number following 999,999,999 and preceding 1,000,000,001. In scientific notation, it is written as 109.