undecillion
C2 (Very low frequency, specialized)Highly specialized/technical; formal
Definition
Meaning
The cardinal number represented by 1 followed by 36 zeros (short scale) or by 1 followed by 66 zeros (long scale).
An extremely large, indefinite number used primarily in mathematics, astronomy, cosmology, and theoretical contexts to denote quantities of a scale that is practically unimaginable in everyday life.
Linguistics
Semantic Notes
This is a cardinal numeral. Its precise value depends on the naming system (short scale vs. long scale). In modern American and British English, the short scale (10^36) is standard. The long scale (10^66) is archaic in English but still used in some European languages. It is virtually never used outside scientific, mathematical, or humorous hyperbolic contexts.
Dialectal Variation
British vs American Usage
Differences
No significant difference in meaning or usage in modern contexts. Historically, the UK used the long scale, but since 1974, British official and scientific usage has aligned with the short scale (10^36), matching the American standard.
Connotations
Identical connotations of an astronomically large, abstract number.
Frequency
Equally rare and specialized in both varieties.
Vocabulary
Collocations
Grammar
Valency Patterns
NUM + of + NP (an undecillion of particles)NUM + NP (an undecillion atoms)Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “Not even an undecillion of... (hyperbolic negation)”
Usage
Context Usage
Business
Virtually never used. Potential hyperbolic use in marketing: 'An undecillion of possibilities.'
Academic
Used in theoretical mathematics, combinatorics, cosmology (e.g., number of potential quantum states in a volume of space), and astronomy (e.g., theoretical particle counts in large volumes).
Everyday
Extremely rare, only for hyperbolic exaggeration or humour.
Technical
The primary domain of use. Precise numerical value in scientific notation or theoretical calculations.
Examples
By Part of Speech
adjective
British English
- The undecillion figure was used in the cosmological model.
- They calculated an undecillion-fold increase.
American English
- An undecillion number of combinations is theoretically possible.
- The undecillion estimate was purely hypothetical.
Examples
By CEFR Level
- The number of atoms in the observable universe is estimated to be under an undecillion.
- In a hyperbolic sense, he said he had an undecillion things to do.
- The total number of possible chess games far exceeds an undecillion, illustrating the game's complexity.
- Certain cosmological theories involve calculations on the scale of undecillions of elementary particles.
Learning
Memory Aids
Mnemonic
Think: 'UNDER a DECILLION is a nonillion, but OVER a decillion is an UN-decilion?' No. Better: It follows 'decillion'. Remember the sequence: Million, Billion, Trillion... Decillion, UNDECILLION. 'Un-' (one) added to the root for ten (deci-), meaning one plus ten = eleven groups of three zeroes? Actually, in short scale, 'undecillion' is the 11th '-illion' term (10^(3*11+3) = 10^36). So 'un-deci-llion' = 'one-ten-illion' = 11th term.
Conceptual Metaphor
QUANTITY IS SIZE / NUMBER IS VERTICAL SCALE (an unimaginably high point on a scale of magnitudes).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Russian uses the long scale system. Therefore, 'undecillion' (ундециллион) in Russian means 10^66, not 10^36. This is a critical false friend in scientific translation. The English short-scale 'undecillion' (10^36) is 'секстиллион' (sextillion) in the Russian long-scale system.
Common Mistakes
- Confusing its value (short vs. long scale).
- Misspelling (e.g., 'undecilion', 'undecilion').
- Using it in non-technical contexts where it is inappropriate.
- Incorrect pluralization ('undecillions' is possible but rare).
Practice
Quiz
In which context is the word 'undecillion' MOST appropriately used?
FAQ
Frequently Asked Questions
In modern English (short scale), it is 10^36, or 1,000,000,000,000,000,000,000,000,000,000,000,000.
Almost never in daily life. Its primary use is in specialized fields like theoretical mathematics, cosmology, and cryptography, where such large numbers are part of formal models or calculations.
In the short scale, the next term is 'duodecillion' (10^39), followed by 'tredecillion' (10^42), and so on.
The difference stems from historical naming systems for large numbers. The short scale (where each new -illion term is 1,000 times the previous) is now standard in English-speaking and Arabic-numeral using countries. The long scale (where each term is 1,000,000 times the previous) was formerly used in British English and is still used in many European languages, leading to translation confusion.