# Entropy

The **Entropy** (or **Shannon entropy**) of a distribution is a measure of its uncertainty.

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A value of zero indicates an outcome that is certain. For example a distribution with evidence set on its variable(s).

The expression **H(X)** is used to denote the entropy of a variable X. X can also represent groups of variables.

The expression **H(X|Z)** is used to denote the conditional entropy of X given Z. Again X or Z can be groups of variables.

## Support

Variable types | Multi-variate | Conditional | Notes |
---|---|---|---|

Discrete | Yes | Yes | Multiple & conditional since 7.12 |

Continuous | Yes | Yes | Since 7.12 |

Hybrid | Yes | Yes | Approximate, since 7.16 |