quadrillion

Quadrillion is a large number name used in mathematics and everyday language to denote a specific quantity. In the short scale, which is standard in the United States and most modern contexts, a quadrillion equals 10^15, that is 1,000,000,000,000,000 — one thousand trillion.

Historically, some European countries used the long scale, in which a quadrillion equals 10^24 (1 followed by 24 zeros). In that system the sequence is million (10^6), milliard (10^9), billion (10^12), trillion (10^18), quadrillion (10^24). Because of these differences, the meaning of quadrillion can vary by region and historical context.

In contemporary usage, most English-language references follow the short scale, so quadrillion typically means 10^15. The term derives from Latin, with quadri- meaning four and the suffix -illion, used to form large-number names.

Representations and related terms: 1 quadrillion equals 1e15 in the short scale and 1e24 in the long scale. It is followed by quintillion (short scale: 10^18). In practical contexts, quadrillions are used in astronomy, national statistics, large-scale economics, and other fields that require expressing extremely large quantities.

Context is important when interpreting the term, as the value depends on whether the short or long scale is in use.