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quadrillion Syllabification: quad·ril·lion
Pronunciation: /kwäˈdrilyən/

Definition of quadrillion in English:

cardinal number (plural quadrillions or (with numeral or quantifying word) same)

1A thousand raised to the power of five (1015).
Example sentences
  • The lesson continues this way up until the quadrillions.
  • Others are known that are so very slightly unstable that their half-lives are trillions and quadrillions of years.
  • Each of them had been coated with quadrillions of luminescent particles.
1.1 dated, chiefly British A septillion, that is, a thousand raised to the power of eight (1024).


Pronunciation: /-ˈdrilyənT͟H/
ordinal number
Example sentences
  • With the neutrons traveling much, much faster, I estimate about 28 percent of the material will go critical in that quadrillionth of a second.
  • In addition, LCLS X-ray pulses will be extremely short - lasting only femtoseconds, mere quadrillionths of a second.
  • A femtosecond is a millionth of a billionth (or one quadrillionth) of a second.


Late 17th century: from French, from million, by substitution of the prefix quadri- 'four' for the initial letters.

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