Betrayal And Loyalty

noun a person who informs on another person or group, especially to the authorities

verb to inform on someone, especially to the authorities

• The informant decided to fink on the criminal activity to the authorities.
• Don't be a fink and tell on your friends for skipping class.
• I can't believe you finked on me like that!
• The dark clouds were like a fink, threatening to ruin the picnic.

noun a person who deserts one party or cause in order to join an opposing one

adjective relating to or characteristic of a turncoat

• The turncoat betrayed his comrades by switching sides during the war.
• I can't believe she's such a turncoat, she was just praising us yesterday.
• Don't trust him, he's a total turncoat.
• Her sudden change of heart made her seem like a turncoat in the eyes of her friends.