ORDER BOOK

An electronic list of buy and sell orders for a specific security or financial instrument, organized by price level. The order book lists the number of shares being bid or offered at each price point, or market depth. It also identifies the market participants behind the buy and sell orders, although some choose to remain anonymous. The order book is dynamic and constantly updated in real time throughout the day. Exchanges such as Nasdaq refer to this order book as the "continuous book." Orders that specify execution only at market open or market are maintained separately. These are known as the "opening (order) book" and "closing (order) book," respectively.