perfidy

American  

[pur-fi-dee] / ˈpɜr fɪ di /

noun

• perfidies
  plural

1. deliberate breach of faith or trust; faithlessness; treachery.

   perfidy that goes unpunished.

2. an act or instance of faithlessness or treachery.

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perfidy British  

/ ˈpɜːfɪdɪ /

noun

1. a perfidious act

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Synonym Usage

See disloyalty.

Other Word Forms

Noun Inflected Forms

• perfidies
  plural

Etymology

Origin of perfidy

1585–95; < Latin perfidia faithlessness, equivalent to perfid ( us ) faithless, literally, through (i.e., beyond the limits of ) faith ( per- per- + fid ( ēs ) faith + -us adj. suffix) + -ia -y ³

Explanation

If you shared your most embarrassing secrets with a friend who then told them to everyone he knows, his betrayal could be described as perfidy. The noun perfidy means "deceitfulness" or "treachery," so it's not just being mean, but deliberately betraying a trust. The Latin root of perfidy is made up of per, or "through," and fidem, or "faith." So in order for perfidy to happen, there has to have first been a sense of faith in place, which was then broken or betrayed.

Example Sentences

See Examples For:

perfidy perfidies

A former JAG and current professor at Texas Tech University, Geoffrey Corn, said the U.S. has considered perfidy a crime in non-international armed conflicts.

From Salon ● Jan. 13, 2026

Jack soon learns, in Robert Penn Warren’s saga of perfidy and corruption, that Gov. Stark is right.

From The Wall Street Journal ● Oct. 23, 2025

Now, those who are convinced of the perfidy of cats won’t like the answers that are emerging.

From New York Times ● Nov. 12, 2022

Bristling and increasingly convinced of Western perfidy and decadence, he was in many respects a changed man.

From Seattle Times ● Mar. 26, 2022

In spite of my perfidy, she was desperate to see me one more time.

From "Harry Potter and the Deathly Hallows" by J.K. Rowling

A famous essay in the Baffler, “The Problem With Music,” laid out the perfidies of the major-label system, at the time still in a post-Nirvana feeding frenzy for young rock acts.

From Los Angeles Times ● May 8, 2024

Swinton Byrne’s own reactions to her fictional lover’s perfidies were more indignant, and less compliant, than what we see onscreen as Julie’s.

From The New Yorker ● May 13, 2019

Gathering up great and infamous political speeches, his juxtapositions compare and contrast passions and perfidies with subtlety and wit, ranging across the French, Flemish, American and German tongues.

From The Guardian ● Aug. 27, 2012

Many of the falsehoods and perfidies I have detailed have come to light since Macaulay wrote, and there are more behind which will appear in their proper place in Pope's life and works.

From The Works of Alexander Pope, Volume 1 New Edition by Alexander Pope

And yet the real reason for the plan remains unstated," said Fossbrooke, looking him steadfastly in the face, "so true is what the Spanish proverb says, 'Love has more perfidies than war.'

From Sir Brook Fossbrooke, Volume II. by Charles James Lever