perfidiousness

noun

"perfidiousness" is a 14-letter English headword indexed on PlainSpell.

The verdict

“perfidiousness” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.

Unranked
below top-frequency English
14
letters

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - Unfaithfulness; deceitfulness; perfidy.

Corpus desk

Index EN-perfidiousness · perfidiousness · English

perfidiousness · unranked · 0 variants · 0 confusables

  • FREQ-UNRANKED Unranked
  • LEN-MEGA 14 letters
  • VOW-6 6 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-THIN "P" thin
  • PHOTO-UNK Peer pending

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Key facts for perfidiousness
PropertyValue
Headwordperfidiousness
LanguageEnglish
Part of speechNoun
Letters14
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “perfidiousness” in English

perfidiousnessfalls outside the top-100,000 ranked English words, the long-tail zone of technical, archaic, or low-frequency vocabulary, exactly where readers second-guess spellings most.

Beyond rank #100,000. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

perfidiousness is uncommon English outside the top frequency list, classed as anoun. Rarity is why readers land here mid-draft. Gloss: "Unfaithfulness; deceitfulness; perfidy.".

Our edit-distance generator produced no likely misspellings for perfidiousness, a sign its spelling follows regular English conventions. Our confusable-pair dataset has no match for it, a sign it's visually distinctive enough not to be mixed up with another word.

Etymologically, the entry records: From perfidious + -ness. The correct English form is perfidiousness, spelled P-E-R-F-I-D-I-O-U-S-N-E-S-S.

Definition

  1. 1
    Unfaithfulness; deceitfulness; perfidy.

Recorded use

Wiktionary example

These source excerpts show how perfidiousness appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. Not only Cato is vanquished by Caesar, but the treachery and perfidiousness of Syphax prevail over the honest simplicity and the credulity of Juba.

Etymology

From perfidious + -ness.

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

How do you spell "perfidiousness"?
"perfidiousness" is spelled P-E-R-F-I-D-I-O-U-S-N-E-S-S.
What does "perfidiousness" mean?
As a noun, "perfidiousness" means: Unfaithfulness; deceitfulness; perfidy.
What is the origin of the word "perfidiousness"?
From perfidious + -ness. See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list