---
title: Information
tags: []
---
# Information

[**information entropy**](https://en.wikipedia.org/wiki/Entropy_(information_theory))
is the expected value of [self-information](https://en.wikipedia.org/wiki/Information_content)
of a random variable:
the expected reduction of uncertainty
when a value of the random variable is revealed.

[units of information](https://en.wikipedia.org/wiki/Units_of_information):
* [**natural unit of information** (symbol **nat**)](https://en.wikipedia.org/wiki/Nat_(unit))
* [**hartley** (symbol **Hart**)](https://en.wikipedia.org/wiki/Hartley_(unit))
* [**shannon** (symbol **Sh**)](https://en.wikipedia.org/wiki/Shannon_(unit))