Surety

n. certainty, assurance; something that is certain; guarantor; pledge, guarantee; guarantor, one who gives a guaranty or security, warrantor, person who provides a guarantee to another

A surety is a person who agrees to be responsible for the debt or obligation of another. Additionally, the situation in which a surety is most typically required is when the ability of the primary obligor or to perform its obligations under a contract is in question, or when there is some public or private interest which requires protection from the consequences of the principal's default or delinquency. In most common law jurisdictions, a contract of suretyship is subject to the statute of frauds (or its equivalent local laws) and is only enforceable if memorialized by a writing signed by the surety.
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Noun
1. something clearly established
(hypernym) certainty, sure thing, foregone conclusion
2. property that your creditor can claim in case you default on your obligation; "bankers are reluctant to lend without good security"
(synonym) security
(hypernym) transferred property, transferred possession
(hyponym) deposit
3. a prisoner who is held by one party to insure that another party will meet specified terms
(synonym) hostage
(hypernym) prisoner, captive
4. one who provides a warrant or guarantee to another
(synonym) guarantor, warrantor, warranter
(hypernym) patron, sponsor, supporter
5. a guarantee that an obligation will be met
(synonym) security
(hypernym) guarantee, warrant, warrantee, warranty

(v. t.)
To act as surety for.
  

(n.)
The state of being sure; certainty; security.
  

(n.)
That which makes sure; that which confirms; ground of confidence or security.
  

(n.)
Security against loss or damage; security for payment, or for the performance of some act.
  

(n.)
One who is bound with and for another who is primarily liable, and who is called the principal; one who engages to answer for another's appearance in court, or for his payment of a debt, or for performance of some act; a bondsman; a bail.
  

(n.)
Hence, a substitute; a hostage.
  

(n.)
Evidence; confirmation; warrant.
  

An individual or corporation that guarantees the performance or actions of another.