Slippage: the price you clicked is not the price you got

Your stop sits 30 pips below your entry. A number is released, and the next quote on your screen is 48 pips below. Your stop filled there, because a stop order becomes a market order when its level trades, and the market's next available price is what a market order gets.

The plan said one loss. The account shows a bigger one. The difference is slippage, and no line on your statement itemises it.

Where does slippage come from?

Module 1's answer: your order needs a counterparty at a price, and prices only exist where dealers quote them. In deep, calm markets the next quote sits a fraction of a pip away and slippage rounds to nothing. Around news, at the weekly open, and in the thin hours, quotes are pulled and re-placed far apart, and your order fills at the first price that exists, not the price you named.

Module 2's calendar lesson marked when this happens. This lesson prices what it costs when it does.

Which orders take slippage, and which refuse it?

Market orders and triggered stops accept the next available price by design, so they take whatever slippage conditions produce. A limit order names its price and will not fill beyond it, so it cannot slip against you. What it can do is fail to fill at all while price runs away. That is the trade module 1's order types lesson set up: certainty of fill against certainty of price. Slippage is the invoice for choosing fill.

When is it a real cost rather than noise?

Day to day, on liquid pairs in liquid hours, slippage is fractions of a pip in both directions and roughly cancels. It stops being noise in exactly the situations you can list in advance: holding a stop through scheduled news, through a weekend, or in a pair whose book is thin at your trading hour. In those, the slippage on one exit can exceed a month of spread costs, and the example below is deliberately one of those.

What this means for you

Treat slippage as a cost you schedule rather than one that ambushes you. The calendar tells you when quotes thin out; holding through those windows is choosing to accept whatever the first price back turns out to be. A stop is a plan for normal markets, and knowing the hours when markets stop being normal is part of knowing what your trade can cost.