Short Definition
Calibration measures whether predicted probabilities match observed frequencies.
Intuition
If a model says 70 percent confidence many times, about 70 percent of those predictions should be correct.
Technical Definition
Calibration compares forecast probabilities with empirical outcome rates, often using reliability diagrams, Brier score, or expected calibration error.
Example
A weather model is calibrated if days with 30 percent rain probability rain about 30 percent of the time.
Common Misunderstandings
Accuracy and calibration are different properties.
A model can be accurate but overconfident.