An amount owed by someone (i.e., the debtor) to another (i.e., the creditor). Also referred to as a liability. Debt owed by a company to a financial institution or an investor in a transaction in which the company does not provide collateral to the lender is unsecured debt. When the debt is secured by collateral, the debt is referred to as secured debt. Common forms of debt securities are notes or bonds. (See subordinated debt.)