ExpertGlossary

The first transaction in each security or commodity when trading begins for the day occurs at what's known as its opening, or opening price.

Sometimes the opening price on one day is the same as the closing price the night before. But that's not always the case, especially with stocks or contracts that are traded in after-hours markets or when other factors affect the markets when the stock or commodity is not trading.

The opening also refers to the time that the market opens for trading or the time a particular instrument begins trading. For example, New York Stock Exchange (NYSE) opens at 9:30 ET. The first transaction in a single security may be at that time or at a later time.