Slippage
The difference between the expected fill price and the actual fill price. Positive slippage benefits you; negative slippage costs you.
Slippage is the gap between the price you intended to trade at and the price you actually received. It is an unavoidable cost in real-world execution, particularly for market orders and during fast or illiquid markets.
Slippage has two sources: bid-ask spread (the structural cost of immediately crossing the spread) and market impact (your own order moving prices as it consumes available liquidity).
Positive slippage occurs when your fill is better than expected — a buy that fills below the ask. Negative slippage is the more common case: a buy that fills above the current ask because liquidity at that level was consumed before your order arrived.
Example
You send a market buy expecting to fill at $50.00. By the time your order reaches the exchange, sellers at $50.00 are gone and you fill at $50.07. Slippage = $0.07 per share.
Related Terms
Bid-Ask Spread
The gap between the highest price a buyer will pay (bid) and the lowest price a seller will accept (ask). Crossing it is the minimum cost of an immediate trade.
BeginnerBlock Trade
A single large transaction — typically 10,000+ shares or $200,000+ in value — usually executed privately to minimize market impact.
AdvancedExecution
The process of completing a trade — from order submission through matching and confirmation. Execution quality affects real-world returns.
BeginnerFill
A confirmed execution of an order — the trade happened, shares changed hands at a specific price and time.
BeginnerImplementation Shortfall
The total cost of executing a trade measured against the price when the decision was made — the gap between paper and realized performance.
AdvancedMarket Depth
The volume of open buy and sell orders at various price levels — a measure of how much size the market can absorb without large price movement.
IntermediateMarket Impact
The adverse price movement caused by your own order consuming liquidity — buying pushes price up, selling pushes it down.
AdvancedMarket Order
An order to buy or sell immediately at the best available price. Guarantees execution but not the fill price.
BeginnerMarketable Limit Order
A limit order priced at or through the current best opposite quote — it acts like a market order but protects against extreme fills.
IntermediateOrder Book
The real-time record of all outstanding buy and sell limit orders for an asset, organized by price level.
BeginnerOrder Flow
The stream of incoming buy and sell orders hitting the market — analysis of order flow reveals who is aggressive and where price is likely headed next.
AdvancedOrder Types
The instructions that tell a broker how to execute a trade — chiefly market, limit, and stop orders, plus their conditions and time-in-force.
BeginnerPrice Improvement
A fill at a better price than the prevailing NBBO — buying below the national ask or selling above the national bid.
IntermediateSmart Order Routing
Automated logic that scans multiple trading venues to find the best price, fee, and fill quality for each order.
AdvancedStop Order
An order that becomes a market order once the asset trades at or through a specified stop price.
BeginnerStop-Limit Order
A two-stage order: a stop price triggers the order, then a limit price caps the worst acceptable fill.
IntermediateStop-Loss Order
A stop order placed to exit a position at a loss before it grows larger. The primary tool for managing downside risk.
BeginnerTaker
A trader whose order immediately executes against a resting limit, removing liquidity from the book and typically paying a fee.
Intermediate