treason |ˈtrēzən|
noun (also high treason)
the crime of betraying one’s country, esp. by attempting to kill the sovereign or overthrow the government : they were convicted of treason.
• the action of betraying someone or something : doubt is the ultimate treason against faith.
• ( petty treason) historical the crime of murdering someone to whom the murderer owed allegiance, such as a master or husband.

DERIVATIVES
treasonous |ˈtrēzənəs| adjective

ORIGIN Middle English : from Anglo-Norman French treisoun, from Latin traditio(n-) ‘handing over,’ from the verb tradere.

USAGE Formerly, there were two types of crime to which the term treason was applied: petty treason (the crime of murdering one’s master) and high treason (the crime of betraying one’s country). As a classification of offense, the crime of petty treason was abolished in 1828. In modern use, the term high treason is now often simply called treason.