betray
v.to hurt someone who trusts you by doing something dishonest or helping their enemy. It can also mean to show a secret or a feeling that you were trying to hide.
v.to violate the confidence of a person or group by providing information or assistance to an adversary; alternatively, to reveal a secret or emotion unintentionally.
“He promised to keep the secret, but he decided to betray her.”
“The spy was caught after he tried to betray his country by selling classified documents to a foreign power.”
“Although she maintained a calm and professional exterior during the negotiation, a slight tremor in her voice began to betray her growing anxiety about the deal's potential collapse.”
The verb is transitive and requires a direct object, such as a person, a cause, or a secret.
Betray is a transitive verb and takes a direct object without a preposition.
“We also see more betrayal here as Ulf (Tom Bennett) decides to betray Rhaenyra and double cross Ormund by burning the market town in spectacular fashion.”
“You betray not only this community, but the national character.”
From Middle English betrayen, bitrayen (“to commit an act of treason against”), equivalent to be- + tray (“to betray”). further etymology information Middle English bi- is from Old English be- (“be-”), from Proto-Germanic bi- (“be-”), from Proto-Germanic bi (“near, by”), ultimately from Proto-Indo-European h₁epi (“at, near”). Compare also traitor, treason, tradition. The modern sense “to disclose, discover, reveal unintentionally” is due to influence from or merger with English bewray (“to reveal, divulge”), which is similar in sound and meaning. The similarity with German betrügen, Dutch bedriegen, from Proto-West Germanic bidreugan (“to betray, deceive”), is coincidental.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.