Treason
From Wikipedia, a free encyclopedia written in simple English for easy reading.
Treason is when a person acts against his country – for example, somebody might help another country fight a war against his country.
Treason is a common word, but different countries have different laws against it.
The word for a person who is treasonous is “traitor”. Some famous traitors are Judas, Benedict Arnold, Pétain and Quisling.