perfidiousness C2+ Topic:Describing Qualities US /pərˈfɪdiəsnəs/ UK /pəˈfɪdiəsnəs/ See IPA manual Meanings 1 noun the quality of being deceitful and untrustworthy His perfidiousness cost him every friend he had. Thesaurus Synonyms 1 noun · the quality of being... treacheryperfidydisloyaltyfaithlessnessbetrayalduplicityfalseness ↔ Opposites loyaltyfidelityfaithfulnesstrustworthiness Word family Related forms perfidiousperfidy Etymology AI details From perfidious (from Latin perfidus 'faithless') + -ness. Perfidus is from per- ('through, away') + fides ('faith'). perfidus Latin fides Latin View etymology graph -> Topics Describing Qualities Word Formation & Derivatives External links Cambridge Dictionary Wiktionary Google Images # perfidiousness **Type:** Word **Level:** C2+ **Part of speech:** noun **IPA (US):** /pərˈfɪdiəsnəs/ **IPA (UK):** /pəˈfɪdiəsnəs/ ## Meanings 1. the quality of being deceitful and untrustworthy ## Examples - His perfidiousness cost him every friend he had. ## Synonyms - treachery - perfidy - disloyalty - faithlessness - betrayal - duplicity - falseness ## Antonyms - loyalty - fidelity - faithfulness - trustworthiness ## Related Forms - perfidious - perfidy ## Roots and Affixes - Root: perfidus - Root: fides ## Etymology From perfidious (from Latin perfidus 'faithless') + -ness. Perfidus is from per- ('through, away') + fides ('faith'). ## AI Etymology Perfidiousness is from perfidious (from Latin perfidus 'faithless') + -ness. Perfidus is from per- ('through, away') + fides ('faith'). Important recorded forms include perfidus (Latin) and fides (Latin). Morphologically, the word preserves a built structure whose named elements carry the historical sense into English. The modern sense remains close to that composition, with the parts narrowing into a single lexical item. In current use it covers the quality of being deceitful and untrustworthy. The wider family includes related words such as perfidious and perfidy. ## Topics - Describing Qualities - Word Formation & Derivatives markdown