Short selling is an investment or trading strategy that speculates on the decline in a stock or other security's price. It is an advanced strategy that should only be undertaken by experienced traders and investors.

Traders may use short selling as speculation, and investors or portfolio managers may use it as a hedge against the downside risk of a long position in the same security or a related one. Speculation carries the possibility of substantial risk and is an advanced trading method. Hedging is a more common transaction involving placing an offsetting position to reduce risk exposure.

In short selling, a position is opened by borrowing shares of a stock or other asset that the investor believes will decrease in value. The investor then sells these borrowed shares to buyers willing to pay the market price. Before the borrowed shares must be returned, the trader is betting that the price will continue to decline and they can purchase them at a lower cost. The risk of loss on a short sale is theoretically unlimited since the price of any asset can climb to infinity.