surety

noun

1. 1

   Certainty.

2. 2

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

3. 3

   A promise to pay a sum of money in the event that another person fails to fulfill an obligation.

4. 4

   One who undertakes to pay money or perform other acts in the event that his principal fails therein.

5. 5

   A substitute; a hostage.

6. 6

   Evidence; confirmation; warrant.