price impact

Price impact is the part of slippage you cause yourself: the amount your own trade shifts a pool's price simply by being executed against finite liquidity. It is the deterministic, calculable component, fixed entirely by the pool's reserves and your order size at the instant of the trade, with no randomness and no adversary involved. Slippage is the broader umbrella that also includes market drift and front-running between quote and fill; price impact is the slice you would suffer even in an otherwise empty block.

On a constant-product curve, price impact grows worse than linearly with order size. A trade that is 1% of the pool's reserves barely moves the price, but a trade that is 50% of the reserves moves it dramatically, because you are climbing a hyperbola that steepens as you deplete one side. Concretely, buying token Y leaves a marginal price of (x + dx)/(y - dy), which always exceeds the starting ratio x/y, and the larger dx is, the bigger that gap. Deeper pools (larger reserves) flatten the curve and shrink price impact for the same dollar trade, which is the whole point of attracting more liquidity.

Traders manage price impact by splitting a large order across time or across many pools, by routing through aggregators that find the deepest path, or by choosing venues whose curve is flatter near the current price — for example a StableSwap pool for like-valued assets, or a concentrated-liquidity range where depth is dense. The displayed 'price impact: 0.8%' warning in a swap interface is the protocol estimating this self-inflicted move so you do not unknowingly execute a trade far too large for the available depth.