Which word refers to the act of betrayal or breach of trust?

The term 'perfidy' specifically refers to the act of betrayal or breach of trust, often highlighting a deliberate act of treachery. It originates from the Latin word "perfida," meaning faithless or treacherous. In contexts where loyalty and fidelity are expected—such as in personal relationships, politics, or contracts—perfidy denotes a deep violation of trust that can have serious emotional or social consequences.

While 'treachery' also conveys a sense of betrayal, it is more of a general term that does not capture the nuances of betrayal as clearly as perfidy does. 'Deceit' involves lying or misleading someone, which is a broader concept that can lead to betrayal but does not inherently denote a breach of trust. 'Duplicity' refers to the quality of being double-dealing or deceitful, implying a two-faced nature but not specifically highlighting the betrayal of trust that perfidy does. Thus, 'perfidy' stands out as the most precise term that directly encapsulates the act of betrayal or breach of trust.