What does quadrillionth mean?
A quadrillionth is an ordinal term denoting one part in 10¹⁵ of a whole. In its strict mathematical sense, it identifies the place reached after dividing a unit into a quadrillion equal parts, equivalent to 10⁻¹⁵. Such quantities occur in discussions of atomic dimensions, ultrafast physical processes, and the theoretical resolution of measurements. The word can also be used informally to emphasize how minute, remote, or unlikely something is, especially in phrases such as “the quadrillionth time.” This figurative use often suggests frustration or amused disbelief rather than a literal mathematical calculation. Because quadrillionth follows the same ordinal pattern as millionth, billionth, and trillionth, it is readily understood by readers familiar with large-number terminology, even though precise scientific writing may prefer a power-of-ten expression.
adjectiveDenoting the ordinal number obtained by placing one in the quadrillionth position, equivalent to 10⁻¹⁵ of a whole. In informal usage, it describes an extremely remote or negligible division of a very large number.
- Denoting the ordinal corresponding to one quadrillionth of a whole.
- Informally, describing a minute, remote, or effectively negligible quantity.
"The precision required to locate a single molecule is on the order of a quadrillionth of a metre."
"The reaction occurred within a quadrillionth of a second."
"By the quadrillionth attempt, the researchers had examined every possible arrangement."
A quadrillionth is so extraordinarily small that it serves as a vivid shorthand for the limits of physical measurement and human precision.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does quadrillionth come from?
The word combines the combining form quadr-, associated with the Latin numerals quadri- and quattuor, meaning “four,” with the English ordinal suffix -illion and the ordinal ending -th. Quadrillion itself was formed in English during the early modern period through the French quadrillion, ultimately from Latin quadrillion, a derivative of quadragintā, meaning “forty.” The progression of the -illion series reflects successive powers of a thousand, with quadrillion denoting 10¹⁵. English later added -th to form the corresponding ordinal.
Related word forms
How quadrillionth is actually used
The word is mathematically exact but uncommon outside scientific, technical, or hypothetical contexts. Its informal use for an extremely tiny amount is rhetorical and may carry a humorous or exaggerated tone.
Easily confused with quadrillionth
A quadrillion is the cardinal number equal to 10¹⁵, whereas the quadrillionth denotes the corresponding minute ordinal division or position.
A quintillion equals 10¹⁸, three orders of magnitude larger than a quadrillion.