Perfidious means deceitful and untrustworthy, often betraying the trust of others.


US English

UK English

Part of Speech

Perfidious is an adjective.


Deceitful, treacherous, untrustworthy, disloyal, faithless.


Trustworthy, loyal, faithful, reliable, dependable.

Word Forms

Part of Speech Words
Noun perfidiousnesses, perfidy, perfidies, perfidiousness
Verb None
Adjective perfidious
Adverb perfidiously

Example Sentences

  • The perfidious politician promised to support his constituents, but he betrayed them once he was elected.

  • The perfidious employee stole confidential information and sold it to a competitor.

  • The perfidious friend revealed secrets to others and undermined trust within the group.

  • The perfidious lover cheated and lied, causing irreparable damage to the relationship.


The word “perfidious” is used to describe people or actions that are deceptive, untrustworthy, or betray the trust of others. It is typically used in situations where there is a breach of loyalty or a violation of trust, such as in politics, business, or personal relationships.

The word “perfidious” comes from the Latin word “perfidia,” which means “faithlessness” or “treachery.” It has a strong negative connotation and is often used in a moral or ethical context.

There are several variations of the word “perfidious” that have slightly different meanings or connotations. For example, the noun “perfidy” can be used to describe an act of betrayal or treachery, while the adverb “perfidiously” can be used to describe behavior or actions that are done in a deceitful or untrustworthy manner.

It’s worth noting that the word “perfidious” is often used in a formal or academic context, such as in legal documents or scholarly papers. It is also used in literature and other forms of creative writing to describe characters or situations that involve deceit or betrayal.

In summary, “perfidious” is a strong and negative adjective that is used to describe people or actions that are deceitful, untrustworthy, or betray the trust of others. It has a long history and is often used in formal or academic contexts, as well as in literature and creative writing.