on the sly
"on-the-sly" is a 8-letter English headword indexed on PlainSpell.
The verdict
“on the sly” is outside the top-ranked English vocabulary, used as an adverb - the kind of word writers most often double-check.
- Unranked
- below top-frequency English
- 10
- letters
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Slyly, in an inconspicuous manner, so as not to be seen; secretly; stealthily.
| Property | Value |
|---|---|
| Headword | on the sly |
| Language | English |
| Part of speech | Adverb |
| Letters | 10 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “on the sly” sits in English frequency
Spelling & Dictionary Insight
The English entry for on the sly is 10 letters long, classified as an adverb. It sits outside the most-frequent rank tiers, which is often why uncommon words generate more spelling variants per reader. The dominant gloss from Wiktionary reads: "Slyly, in an inconspicuous manner, so as not to be seen; secretly; stealthily.".
No misspelling variants are generated for on the sly in our index, since its letter sequence doesn't invite the usual edit-distance slips. This entry stands alone in our confusable dataset, which typically means the spelling is too distinctive to be mistaken for another word.
This entry carries no recorded etymology, so its spelling is easiest to reason about phoneme by phoneme, absent a documented history. The correct English form is on the sly, spelled O-N- -T-H-E- -S-L-Y.
Definition
- 1Slyly, in an inconspicuous manner, so as not to be seen; secretly; stealthily.
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 “on the sly”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is O-N- -T-H-E- -S-L-Y - 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.