What does perfidiously mean?
Perfidiously is a formal adverb describing conduct that betrays a trust or promise through deliberate deception or disloyalty. It is stronger and more accusatory than words such as dishonestly, because it implies a violation of faith, not merely an attempt to gain an advantage by lying or cheating. The word is especially appropriate for describing betrayal by an ally, subordinate, adviser, or public official, and for actions that undermine confidence in an institution or relationship. Perfidious behavior suggests intentional treachery and moral culpability, rather than carelessness, incompetence, or an unfortunate mistake. Because of its grave connotation, perfidiously is commonly used in legal, political, journalistic, and literary contexts. It is also related to the Latin root found in perfidy and perfidious, both of which express the idea of faithlessness or treachery.
adverbIn a perfidious manner; in breach of trust or faith, especially by betrayal or deceit.
- In a treacherous or disloyal manner; betraying trust or faith.
- With deliberate deceit or bad faith.
"The diplomat acted perfidiously, sharing confidential information with an adversary."
"The adviser perfidiously manipulated the committee to secure a private advantage."
"Her perfidious conduct undermined confidence in the organization."
Perfidiously captures the particular harm of betraying a trust that someone had honestly given you.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does perfidiously come from?
The word comes through French from Latin perfidiosus, meaning “treacherous” or “ faithless,” with the related noun perfidia meaning “treachery.” Its underlying elements are per-, meaning “through” or “beyond,” and fidus, meaning “faithful,” giving the idea of faithlessness or breach of trust. The adverbial form perfidiously developed as a manner adverb from perfidious and has been used in English since the early 17th century.
Related word forms
How perfidiously is actually used
Perfidiously is formal and strongly condemnatory. It commonly describes betrayal, deception, or disloyalty rather than ordinary mistakes or unsuccessful actions.
Easily confused with perfidiously
Perfidiously describes deliberate betrayal or deceit, whereas perfunctorily describes something done without care or genuine interest.