noun
pledge, in this comparison, applies to anything given as security for the performance of an act or contract or for the payment of a debt he gave her a ring as a pledge; earnest applies to anything given or done as an indication, promise, or assurance of more to follow her early triumphs are an earnest of her success; token is used of anything serving or given as evidence of authority, genuineness, good faith, etc. this watch is a token of our gratitude; pawn now usually refers to an article left as security for the money lent on it by a pawnbroker; hostage is applied to a person handed over as a pledge for the fulfillment of certain terms or one seized and kept to force others to comply with demands
See pledge in Webster's New World Roget's A-Z Thesaurus II
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