A more thorough explanation:

A subordinate debenture is a type of debt instrument that is lower in priority than other types of debt. It is a type of debenture, which is a bond that is backed only by the general credit and financial reputation of the corporate issuer, not by a lien on corporate assets.

For example, if a company issues both ordinary debentures and subordinate debentures, the ordinary debentures would be paid off first in the event of bankruptcy or default. The subordinate debentures would only be paid off after the ordinary debentures and other types of debt have been paid.

Another type of debenture is a convertible debenture, which can be changed or converted into some other security, such as stock. A convertible subordinated debenture is a debenture that is subordinate to another debt but can be converted into a different security.

A sinking-fund debenture is a debenture that is secured by periodic payments into a fund established to retire long-term debt. This type of debenture helps ensure that the company has the funds to pay off its debt when it becomes due.

In English law, a company's security for a monetary loan is also called a debenture. The security usually creates a charge on company stock or property.

Overall, subordinate debentures are a type of debt instrument that is lower in priority than other types of debt. They are a way for companies to raise funds, but investors should be aware that they may not be paid off first in the event of bankruptcy or default.