# treachery

/ˈtɹɛtʃɝi/ (US) · /tɹˈɛtʃəɹi/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/treachery
Updated: 2026-05-08

## Definition

the act of hurting someone who trusts you, often by helping their enemies. It is a very serious form of lying or betrayal.

For teachers: the betrayal of trust or a deceptive action that violates an established allegiance. Often carries a literary or historical tone, implying a grave moral failing.

## Examples

- He was shocked by his friend's treachery.
- The general was executed for treachery after he secretly sold military secrets to the opposing army.
- The novel explores the psychological toll of treachery, showing how a single act of betrayal can dismantle a community's social fabric and lead to decades of resentment.

## Usage notes

- Uncountable when referring to the quality of being treacherous; countable when referring to specific acts of betrayal.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.