Definition

1. Noun:
   • A very large number: In the short scale system (used in most English-speaking countries, including the United States), a quadrillion is the number represented as 1 followed by 15 zeros (10^15 or 1,000,000,000,000,000).
   • A different very large number: In the long scale system (historically used in some European countries, including the UK), a quadrillion is the number represented as 1 followed by 24 zeros (10^24).

Usage

• The meaning of "quadrillion" depends on the numerical naming system being used. The short scale is now standard in modern British English and American English. The long scale definition is largely historical.
• It is used to express extremely large quantities, often in scientific, financial, or astronomical contexts.

Examples

• Short Scale (10^15):
  • Scientists estimate the number of ants on Earth is in the quadrillions.
  • The national debt reached several quadrillion units of the local currency after the economic crisis.
• Long Scale (10^24) - Historical/Contextual:
  • In some 19th-century British texts, a quadrillion meant a number with 24 zeros.

Advanced Usage

• "Quadrillionth" (ordinal number and noun): Constituting number quadrillion in a sequence; one of a quadrillion equal parts.
  • This event happens only once in a quadrillion years. (ordinal)
  • A quadrillionth of a meter is a femtometer. (noun, fraction)

Variants and Related Words

• Quadrillionfold (adverb): By a factor of one quadrillion.
  • The computing power increased quadrillionfold over the century.

Synonyms

• 10^15 (Short Scale): One thousand trillion (US/Modern UK).
• 10^24 (Long Scale): One septillion (US/Modern UK).

Notes on Numerical Scales

• Short Scale: Each new term greater than a million is 1,000 times the previous term (billion=10^9, trillion=10^12, quadrillion=10^15).
• Long Scale: Each new term greater than a million is 1,000,000 times the previous term (billion=10^12, trillion=10^18, quadrillion=10^24).

Noun

1. the number that is represented as a one followed by 15 zeros
2. the number that is represented as a one followed by 24 zeros
   • in England they call a septillion a quadrillion