zalog

1. pledge; pawn; collateral
   Ostavio je sat u zalog. — He left his watch as a pledge.
   Banka traži stan kao zalog za kredit. — The bank wants the apartment as collateral for the loan.
2. pledge; token; guarantee
   Obrazovanje je zalog za bolju budućnost. — Education is the key to a better future.
   Prsten je bio zalog njihove ljubavi. — The ring was a token of their love.

Usually used in the phrases dati/ostaviti u zalog 'to give/leave as a pledge'.