Book
a.k.a. Trading book, Order book
A dealer's full set of open positions, or the list of buy and sell orders waiting at each price.
In plain English
A dealer's full set of open positions, or the list of buy and sell orders waiting at each price.
Traders use book in two ways. A dealer's book is everything they currently hold: 'I've got a long euro book.' An order book is the live list of resting bids and offers at each price level on a venue.
Brokers also talk about A-book and B-book: passing client trades on to the market, versus keeping them in-house and taking the other side. Knowing which one your broker does helps you understand its incentives.
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