Final answer:
An indenture is the written agreement that details the purchase of a debt security, such as a bond, which is a financial contract committing the borrower to repay the borrowed amount with interest.
Step-by-step explanation:
The agreement in writing containing the details related to the purchase of a debt security is known as an indenture. A bond is a type of debt security and a financial contract where a borrower, such as a corporation, municipality, state, or the federal government, agrees to repay the borrowed amount plus interest over a future period of time. Bonds are similar to bank loans in that they both involve borrowing money and paying interest, but bonds require the borrower to persuade a number of bondholders rather than a single bank.