betray

Etymology

From Middle English betrayen, betraien, 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.

verb

1. (transitive) To deliver into the hands of an enemy by treachery or fraud, in violation of trust; to give up treacherously or faithlessly.
   an officer betrayed the city
2. (transitive) To prove faithless or treacherous to, as to a trust or one who trusts; to be false to; to deceive.
   to betray a person or a cause
   Quresh betrayed Sunil to marry Nuzhat.
   My eyes have been betraying me since I turned sixty.
3. (transitive) To violate the confidence of, by disclosing a secret, or that which one is bound in honor not to make known.
4. (transitive) To disclose or indicate, for example something which prudence would conceal; to reveal unintentionally.
   Though he had lived in England for many years, a faint accent betrayed his Swedish origin.
   Jones’ sad eyes betray a pervasive pain his purposefully spare dialogue only hints at, while the perfectly cast Brolin conveys hints of playfulness and warmth while staying true to the craggy stoicism at the character’s core. May 24, 2012, Nathan Rabin, “Film: Reviews: Men In Black 3”, in The Onion AV Club
   Again, to take a less extreme example, there is no denying that although the dialects of northern France retained their fundamentally Romance character, they betray many Germanic influences in phonetics and vocabulary, … 1966, Marc Léopold Benjamin Bloch, French rural history
5. (transitive) To mislead; to expose to inconvenience not foreseen; to lead into error or sin.
6. (transitive) To lead astray; to seduce (as under promise of marriage) and then abandon.