Expected value (EV)
Expected value is what an action wins or loses on average if the same spot were played many times.
EV weighs every outcome by how often it happens. A call of 3 bb into a pot of 9 bb with 40% equity is worth 0.4 × 12 − 3 = +1.8 bb at showdown.
A play with positive EV can lose this time and still be correct. Comparing the EV of your options, not the result of one hand, is how decisions are judged.
Related terms
Practise decisions like this in the trainer: ten hands at a time, with the answer and the reason.