perfidious.
Of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.
Meaning & usage
Of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.
Where this word comes from
Etymology tree Proto-Indo-European *per- Proto-Italic *per Latin per Proto-Indo-European *bʰeydʰ-der. Latin fidēs Proto-Indo-European *-ós Proto-Indo-European *-os Proto-Indo-European *-ós Proto-Indo-European *-ós Proto-Indo-European *-ós Proto-Indo-European *-ós Proto-Indo-European *-os Proto-Italic *-os Archaic Latin -os Latin -us Latin perfidus Proto-Indo-European *-(i)yós Proto-Italic *-ijos Proto-Italic *-ios Old Latin -ios Latin -ius Latin -ia Latin perfidia Proto-Indo-European *h₃ed- Proto-Indo-European *-os Proto-Indo-European *h₃édosder.? Proto-Italic *-ŏ̄dsos? Old Latin -ōssus Latin -ōsus Latin perfidiōsusbor. English perfidious From Latin perfidiōsus (“treacherous”), from perfidia. By surface analysis, perfidy + -ous.
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Definitions, grammatical labels, IPA, etymology and examples: Wiktionary contributors, extracted by Kaikki / Wiktextract. Adapted under CC BY-SA 4.0. Selected fields and authored examples are shown; third-party quotations and audio are omitted. See contributor history.
Last enriched 2026-09-10. Definitions are in English. Romanizations are shown when supplied by the source; syllable estimates are omitted for unsupported scripts.