A stop-loss is an order that automatically closes a trade once the price reaches a predetermined level, limiting further losses if the market moves against you. It's one of the most fundamental risk-management tools in trading, letting you define your maximum acceptable loss before you even enter a position.
In fast or illiquid markets a stop-loss can still suffer slippage and fill at a worse price than set, unless it's a guaranteed stop (usually offered for an extra fee).
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