perfidious
/pɚˈfɪdi.əs/
"perfidious" is a 10-letter English headword indexed on PlainSpell.
The verdict
“perfidious” is uncommon English (frequency #85,638 among 46,516 “P” headwords), classed as an adjective. The kind of spelling people second-guess.
- #85,638
- frequency rank, English
- 46,516
- “P” headwords
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.
| Property | Value |
|---|---|
| Headword | perfidious |
| Language | English |
| Part of speech | Adjective |
| IPA | /pɚˈfɪdi.əs/ |
| Letters | 10 |
| Frequency rank | #85,638 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “perfidious” sits in English frequency
Rare enough to double-check
perfidious is uncommon English at frequency #85,638 among 46,516 “P” headwords, classed as anadjective, transcribed /pɚˈfɪdi.əs/. Rarity is why readers land here mid-draft. Gloss: "Of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.".
Zero misspellings are on record for perfidious in our index, and the word's spelling is regular enough that our generator found nothing worth flagging. This headword has no recorded confusable partner, which typically means the spelling is too distinctive to be mistaken for another word.
Etymologically, the entry records: From Latin perfidiōsus (“treacherous”), from perfidia. The correct English form is perfidious, spelled P-E-R-F-I-D-I-O-U-S.
Definition
- 1Of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.
Etymology
From Latin perfidiōsus (“treacherous”), from perfidia.
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); 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 “perfidious”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is P-E-R-F-I-D-I-O-U-S - every other letter order is a misspelling in standard orthography.
- Say it as /pɚˈfɪdi.əs/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
- 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.