What significant performance disparity is a hallmark symptom of overfitting?

Answer

A significant gap between very low error on training data and high error on test or validation data.

The defining characteristic of overfitting is the divergence in performance metrics: the model appears nearly perfect on the data it has studied, but its performance degrades significantly when faced with data it has never encountered.

What significant performance disparity is a hallmark symptom of overfitting?
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