# epistemic uncertainty

CEFR C1 · Noun

Source: https://englishreference.com/word/epistemic-uncertainty
Updated: 2026-09-28

## Definition

uncertainty caused by a lack of knowledge or data, which can be reduced by collecting more information.

For teachers: reducible uncertainty in statistical and neural models stemming from insufficient training data or incomplete parameter specification.

## Examples

- The doctor had epistemic uncertainty because the patient's medical history was incomplete.
- Active learning systems query human experts specifically on examples where model epistemic uncertainty is highest.
- Bayesian neural networks explicitly quantify epistemic uncertainty by maintaining a posterior distribution over network weights.

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