Which term mainly refers to the assurance to repay a lent amount?

The term that primarily refers to the assurance to repay a lent amount is best represented by the concept of a creditor. A creditor is an individual or institution that lends money or extends credit to another party. In this context, the creditor is the entity that expects repayment based on an agreed-upon timeframe and terms. The assurance to repay is essentially built into the relationship between the creditor and the borrower (debtor).

The other terms are related but do not specifically denote assurance to repay in the same way. For instance, debtor refers to the individual or entity that has borrowed money and owes a debt, but it does not encapsulate the concept of assurance. Collateral involves property or assets pledged against a loan, providing security to the creditor but is not a direct assurance to repay in itself. A loan agreement is a document that outlines the terms of the loan, including repayment assurances, but it does not represent the concept of assurance as an entity in the same way that the creditor does.