perfidious

UK: /pəˈfɪd.i.əs/ | US: /pərˈfɪd.i.əs/

Definition

  1. adj. deceitful and untrustworthy

  2. adj. deliberately faithless; treacherous

Structure
per <through/completely>fid <faith>ious <adjective suffix>per <through/completely>fid <faith>ious <adjective suffix>
Etymology

Derived from Latin perfidia (treachery), combining per- (thoroughly) and fides (faith). The word evolved to describe someone who "completely breaks faith," emphasizing deliberate betrayal. The suffix -ious later solidified its adjectival form in English, retaining its vivid connotation of calculated dishonesty.

Examples

  1. The perfidious ally abandoned his comrades during the battle.

  2. Her perfidious actions shattered years of trust.

  3. History remembers him as a perfidious ruler who broke every treaty.

  4. The spy's perfidious behavior endangered countless lives.

  5. Detecting perfidious motives early can prevent disasters.