billion

Billion is a term used for a very large number, but its exact value has varied with time and country. In the short scale, which is now standard in most English-speaking contexts, a billion equals 1,000,000,000 (10^9). In the traditional long scale used in parts of Europe, a billion equals 1,000,000,000,000 (10^12). Because of this difference, the word can cause ambiguity without context.

The word derives from Old French billion, formed from bi- (“two”) and a suffix related to the word for large quantity, i.e., a number beyond a million. The long-scale form originally implied a quantity equal to a million millions, while the short-scale form aligns with one thousand millions. The shift in usage over the 19th and 20th centuries led to divergent meanings in different languages and regions.

In modern technical and scientific writing, the SI prefixes are preferred for precision: giga- denotes 10^9, and tera- denotes 10^12. In everyday or financial contexts, people may still encounter different meanings depending on the country; in particular, British usage historically differed from American usage until the mid-20th century when Britain largely adopted the short scale.

Related terms to understand the scale include milliard (10^9 in the long scale) and trillion (10^12 in the short scale; 10^18 in the long scale). Awareness of the two numbering systems helps avoid miscommunication in international data, economics, and media reporting.