An operating mode for stocks, futures and other markets. Short selling refers to the expectation that the market will fall in the future, selling the stock at the current price, and buying it after the market falls to obtain a profit from the price difference. Its trading behavior is characterized by selling first and then buying.

Subordinated debt refers to a special form of debt whose repayment order is superior to the company's equity but lower than the company's general debt (including senior debt and secured debt). The subordination of subordinated debt only refers to the order of debt repayment. If the company enters bankruptcy repayment proceedings, the company can only use the remaining funds to repay such subordinated debts after repaying all its general debts (senior debts). At present, most international subprime bonds are issued by large commercial banks. Since the 1980s, fierce competition among commercial banks has led to a decline in bank capital adequacy ratios and intensified risks in the entire banking industry. In order to prevent risks in the banking industry, the Basel Committee on Banking Supervision promulgated the Basel Accord in July 1988. The core content of the agreement is that the capital adequacy ratio of banks must reach at least 8%. To achieve this goal, one is to increase capital, and the other is to adjust the asset portfolio, select assets with smaller risk weights or reduce the total asset size. The most effective way to improve bank capital adequacy ratios in the short term is to replenish capital. According to the agreement, bank capital consists of Tier 1 capital and Tier 2 capital. Tier 1 capital is core capital, consisting of common shares and public reserves. Secondary capital, also known as auxiliary capital, consists of non-public reserves, asset revaluation reserves, general reserves, hybrid capital instruments and subordinated long-term debt. Since subordinated long-term debt has the characteristics of both debt and equity, it can be used to supplement capital. As an integral part of bank capital, the issuance of subordinated debt can also reduce the average cost of capital, increase shareholder returns, etc.