Hartley function

Etymology
Introduced by in 1928.

Proper noun

 * 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 $$ H_0(A) := \mathrm{log}_b \vert A \vert$$, where $$\vert A \vert$$ denotes the cardinality of A.