-illion
"illion" is a 6-letter English headword indexed on PlainSpell.
The verdict
“-illion” is uncommon English (outside the top frequency list), classed as a suffix. The kind of spelling people second-guess.
- Unranked
- below top-frequency English
- 7
- letters
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Combined with Latin prefixes for names of integers in order to form names of powers of a million.
| Property | Value |
|---|---|
| Headword | -illion |
| Language | English |
| Part of speech | Suffix |
| Letters | 7 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “-illion” sits in English frequency
Rare enough to double-check
-illion is uncommon English outside the top frequency list, classed as asuffix. Rarity is why readers land here mid-draft. 2 senses are on record.
-illion doesn't appear in our generated misspelling index, a sign its spelling follows regular English conventions. No confusable counterpart is on file for this word, which typically means the spelling is too distinctive to be mistaken for another word.
Etymologically, the entry records: Back-formation from million, then used in billion, trillion, quadrillion, each from French, ultimately from Italian mille (“thousand”) and the augmentative suffix -one. -illion was segmented from million as if mi- was a prefix, and -illion the stem. The correct English form is -illion, spelled --I-L-L-I-O-N.
Definition
- 1Combined with Latin prefixes for names of integers in order to form names of powers of a million.
- 2Added to various nonsense syllables to indicate an arbitrarily very large number.
Etymology
Back-formation from million, then used in billion, trillion, quadrillion, each from French, ultimately from Italian mille (“thousand”) and the augmentative suffix -one. -illion was segmented from million as if mi- was a prefix, and -illion the stem.
This word in other languages
Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA). See the methodology for how each field is sourced and updated.
Frequently Asked Questions
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Using “-illion”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is --I-L-L-I-O-N - every other letter order is a misspelling in standard orthography.
- Browse more English words and confusable pairs in the same reference. English words
Data Source
Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.