surety

1 a formal agreement to fulfill an obligation <gave his surety that he would pay back the loan if his sister was unable to for any reason> Synonyms bond, contract, covenant, deal, guaranty, guarantee, warrantyRelated Words oath, pledge, troth, vow, word; accord, bargain, compact, concordat, convention, pact, treaty; assurance, insurance, seal; bail, deposit, pawn, security

2 a person who takes the responsibility for some other person or thing <a mutual friend agreed to act as surety if I lent my cousin some money, since I wasn't certain that she'd be able to pay it back> Synonyms backer, guarantor, patron, sponsorRelated Words chaperone (or chaperon); advocate, champion, supporter; angel, benefactor, underwriter; coach, mentor, teacher; cosponsor; cosignatory, cosigner

3 a state of mind in which one is free from doubt <I can't tell you the year in which that event happened with any great surety> Synonyms assurance, assuredness, certainty, certitude, cocksureness, conviction, doubtlessness, face, positiveness, satisfaction, sureness, confidenceRelated Words authoritarianism, dogmatism; decisiveness, determination, firmness, purposefulness, resoluteness, resolution, resolveNear Antonyms hesitancy, hesitation, indecisiveness, irresolution; disbelief, incredulity, unbelief; anxiety, concern, misgiving; distrust, mistrust, suspicionAntonyms doubt, incertitude, nonconfidence, uncertainty