1,000,000,000 (one billion, short scale; one thousand million or milliard, yard,[1] long scale) is the natural number following 999,999,999 and preceding 1,000,000,001. One billion can also be written as b or bn.[2][3]

CardinalOne billion (short scale)
One thousand million, or one milliard (long scale)
OrdinalOne billionth (short scale)
Factorization29 · 59
Greek numeral
Roman numeralM

In standard form, it is written as 1 × 109. The metric prefix giga indicates 1,000,000,000 times the base unit. Its symbol is G.

One billion years may be called an eon in astronomy or geology.

Previously in British English (but not in American English), the word "billion" referred exclusively to a million millions (1,000,000,000,000). However, this is no longer common, and the word has been used to mean one thousand million (1,000,000,000) for several decades.[4]

The term milliard can also be used to refer to 1,000,000,000; whereas "milliard" is rarely used in English,[5] variations on this name often appear in other languages.

In the South Asian numbering system, it is known as 100 crore or 1 arab.

1,000,000,000 is also the cube of 1000.

Visualization of powers of ten from one to 1 billion