# Hartley function

> English word · Proper noun

## Definitions
1. A measure of uncertainty. If a sample from a finite set A uniformly at random is picked, the information revealed after the outcome is known is given by the Hartley function H_0(A):=log_b|A|, where |A| denotes the cardinality of A.

## Etymology
Introduced by Ralph Hartley in 1928.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/hartley-function