# Definition:Strictly Decreasing/Mapping

## Definition

Let $\left({S, \preceq_1}\right)$ and $\left({T, \preceq_2}\right)$ be ordered sets.

Let $\phi: \left({S, \preceq_1}\right) \to \left({T, \preceq_2}\right)$ be a mapping.

Then $\phi$ is strictly decreasing if and only if:

$\forall x, y \in S: x \prec_1 y \implies \phi \left({y}\right) \prec_2 \phi \left({x}\right)$

Note that this definition also holds if $S = T$.

## Also known as

A strictly decreasing mapping is also known as a strictly order-reversing mapping.

## Also see

• Results about strictly decreasing mappings can be found here.