English Reference
noun

treason

n.
US /ˈtɹizən/ UK /tɹˈiːzən/ trea·son UK spelling treasons

  1. 01 C1 Advanced Formal Law

    the crime of helping your country's enemies or trying to destroy its government.

    the criminal act of betraying one's own nation, especially by attempting to overthrow the government or assisting an enemy during wartime.

    Simple

    The soldier was found guilty of treason for selling secret documents to the enemy.

    In context

    The high court deliberated for weeks before convicting the former official of high treason for his role in the failed coup attempt.

    Usage

    Often used in the phrase 'high treason' to describe the most serious level of the crime.

    Teacher's tip

    In modern legal contexts, this is a very specific and rare charge; in casual conversation, it is often used hyperbolically to describe any major betrayal.

    seditionbetrayaldisloyalty
  2. 02 C2 Proficiency Literary

    a major act of being disloyal to someone who trusts you.

    a violation of allegiance or of faith and confidence; a figurative extension of the legal crime to personal relationships.

    Simple

    To many fans, the captain's decision to join a rival team felt like a personal treason.

    In context

    She viewed his sudden silence not merely as a misunderstanding, but as a profound treason against their decade-long friendship.

    Teacher's tip

    This sense is more common in literature or dramatic speech than in everyday functional English.

    treacheryperfidyduplicity

To punish the rebels for their treason, Parliament passed the New England Restraining Act of 1775, banning locals from fishing in the Atlantic Ocean.

Smithsonian Magazine· 22 Jun 2026

Traditionally, treason and traitor comes with a death sentence, historically.

The Guardian· 11 Aug 2026

From Middle English tresoun, treison, from Anglo-Norman treson, from Old French traïson (“treason”), from trair, or from Latin trāditiō (“a giving up, handing over, surrender, delivery, tradition”), from trādō (“give up, hand over, deliver over, betray”, verb), from trāns- (“over, across”) + dō (“give”). Doublet of tradition.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin trāditiō
Level C1 · Advanced
Frequency Frequent
Updated