IOU
"iou" is a 3-letter English headword indexed on PlainSpell.
The verdict
“IOU” is uncommon English (frequency #69,965 among 17,902 “I” headwords), classed as a phrase. The kind of spelling people second-guess.
- #69,965
- frequency rank, English
- 17,902
- “I” headwords
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - I owe you.
| Property | Value |
|---|---|
| Headword | IOU |
| Language | English |
| Part of speech | Phrase |
| Letters | 3 |
| Frequency rank | #69,965 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “IOU” sits in English frequency
Rare enough to double-check
IOU is uncommon English at frequency #69,965 among 17,902 “I” headwords, classed as aphrase. Rarity is why readers land here mid-draft. Gloss: "I owe you.".
Zero misspellings are on record for IOU in our index, since its letter sequence doesn't invite the usual edit-distance slips. Our confusable-pair dataset has no match for it, which tends to mean the word is visually distinctive enough to stand on its own.
Etymologically, the entry records: From the pronunciation of "I owe you". Attested since at least 1618. The correct English form is IOU, spelled I-O-U.
Definition
- 1I owe you.
Etymology
From the pronunciation of "I owe you". Attested since at least 1618.
Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.
Frequently Asked Questions
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Using “IOU”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is I-O-U - every other letter order is a misspelling in standard orthography.
- Browse more English words and confusable pairs in the same reference. English words
Other uncommon English words near this rank
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.