perfidious C1 Topic:Describing Qualities US /pɚˈfɪdiəs/ UK /pəˈfɪdiəs/ See IPA manual Meanings 1 adj deceitful and untrustworthy He was a perfidious ally, betraying us at the first opportunity. Thesaurus Synonyms 1 adj · deceitful and untrustworthy treacherousdisloyalunfaithfulduplicitousinsidious ↔ Opposites loyalfaithfultrustworthyhonest Etymology AI details From Latin per- ('through') + fidere ('to trust'), forming perfidus ('faithless; treacherous'); via Old French perfide into Middle English perfidious 'deceitful; treacherous'. Topics Describing Qualities Word Formation & Derivatives External links Cambridge Dictionary Wiktionary Google Images # perfidious **Type:** Word **Level:** C1 **Part of speech:** adj **IPA (US):** /pɚˈfɪdiəs/ **IPA (UK):** /pəˈfɪdiəs/ ## Meanings 1. deceitful and untrustworthy ## Examples - He was a perfidious ally, betraying us at the first opportunity. ## Synonyms - treacherous - disloyal - unfaithful - duplicitous - insidious ## Antonyms - loyal - faithful - trustworthy - honest ## Etymology From Latin per- ('through') + fidere ('to trust'), forming perfidus ('faithless; treacherous'); via Old French perfide into Middle English perfidious 'deceitful; treacherous'. ## AI Etymology Perfidious comes from Latin per- ('through') + fidere ('to trust'), forming perfidus ('faithless; treacherous'); via Old French perfide into Middle English perfidious 'deceitful; treacherous'. In current use it is an adjective meaning "deceitful and untrustworthy". That sense is explained by the older material without requiring a speculative semantic step: the inherited or borrowed base supplies the field of meaning, while the English formation fixes its modern role. The surface form is compositional: its joined elements remain visible in the modern word. The word's history is thus visible in its construction: the components remain interpretable even after the whole expression has settled into a conventional English meaning. ## Topics - Describing Qualities - Word Formation & Derivatives markdown