What does sextillionth mean?
A sextillionth is the ordinal corresponding to a sextillion. In the short scale, a sextillion equals 10^21, so the sextillionth denotes the place after 10^21 members of a sequence. In the long-scale system, the same expression corresponds to 10^18. Although the term can describe an exact mathematical position, it is used far more often figuratively to emphasize extreme magnitude, repetition, or insignificance. Phrases such as “for the sextillionth time” convey that something has happened an incomprehensibly large number of times, while descriptions involving the “sextillionth part” invoke an almost vanishing quantity. The word is formal and uncommon in everyday conversation, but it is especially effective when discussing the vast scales found in astronomy, physics, or extended time. Its spelling can also cause confusion with the cardinal noun “sextillion,” which names the number itself rather than its place in an ordered series.
adjectiveThe sextillionth member of a sequence, equivalent to 10^21 in the short scale. In long-scale usage, it corresponds to 10^18.
- Denoting the ordinal number reached after 10^21 members of a sequence, especially in the short scale.
"The universe contains an estimated sextillionth of a second has elapsed since the Big Bang."
"The clock's second hand had completed the sextillionth division of its scale."
"There are enough cosmic photons in the observable universe to outnumber the sextillionth place in a sequence of seconds."
In the short scale, the sextillionth is a number with one followed by 21 zeros—and then a th.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sextillionth come from?
The word combines the ordinal suffix -th with sextillion, which in turn derives from the Latin sex, meaning “six,” together with the numerical suffix -illion. The extended forms -illion, -illiard, and -illion historically denoted successive multiples of a thousand within the traditional long-scale system. English later adopted the short scale for these large numbers, making sextillion equal to 10^21. Related English words such as sextant and sextet also trace to Latin sex, although their development followed separate historical paths.
How sextillionth is actually used
The value depends on the numbering system: it is 10^21 under the short scale, traditionally dominant in the United States and also standard in contemporary British usage, but 10^18 under the long scale. The word is chiefly formal or mathematical and is normally used in figurative expressions of unimaginable magnitude.
Easily confused with sextillionth
A sextillion is the cardinal number 10^21 in the short scale, whereas a sextillionth is the corresponding ordinal number.