Expectancy is the average net profit or loss per trade across a track record: total net P&L divided by number of trades. A positive expectancy means the strategy makes money on average per trade, net of every cost applied; a negative expectancy means it loses money on average, no matter how the win rate or profit factor look individually.
It's arguably the single cleanest summary statistic for whether an edge actually exists, net of reality, since it's already netted against real trading costs rather than shown as a gross, pre-cost number.
Every one of zengtrade's Forward Test and go-live evidence gates includes a positive-expectancy requirement specifically because it's possible to pass a win-rate or trade-count bar while still having an expectancy at or below zero once real costs are applied. A strategy with non-positive expectancy has no business being recommended to anyone, regardless of what its other numbers say.
Educational content, not investment advice. zengtrade is paper-first and non-custodial.