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quadrillion

/kwəˈdrɪljən/

The number one followed by fifteen zeros

From Latin, transmitted through French quadri (four) + French illion (Large-number naming suffix).

noun
quadri
Latin
Verified
quadrī
A form connected with the idea of four

from French quadrillion (16c.)

+1 more source
French
Verified
quadri-
Combining form meaning “four”

from French quadrillion (16c.)

+1 more source
French, 16th century
Verified
quadri-
Used as the numerical prefix in quadrillion

from French quadrillion (16c.)

+1 more source
illion
French
Verified
-illion
Large-number suffix associated with million and related formations

from French quadrillion (16c.)

+1 more source
French, 16th century
Verified
-illion
Suffix used to build names for successively large numbers

from French quadrillion (16c.)

+1 more source
Combined
French quadrillion
The prefix quadri- (“four”) combines with -illion in French; English adopted the resulting number name in the 1670s.
English, 1670s
Verified
quadrillion
A very large-number noun, later standardized differently in short- and long-scale systems

from French quadrillion (16c.)

+1 more source
Modern English
quadrillion

A quadrillion begins with a very ordinary idea: four. The French prefix quadri- was attached to the number-building suffix -illion, producing quadrillion in the sixteenth century; English was using it by the 1670s. Here is the numerical trap: in modern American usage, a quadrillion is 10¹⁵, while traditional British long-scale usage made it 10²⁴—the fourth power of a million. That means an American quadrillion has fifteen zeros, whereas the older British version has twenty-four: same word, nine extra zeros hiding behind the Atlantic. The prefix is the same family found in quadruped and quadrilateral, so whenever you see quadrillion, picture four marching into a crowd of illions and making the crowd unimaginably large.

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