# Definition:Partial Ordering

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## Definition

Let $\struct {S, \preceq}$ be an ordered set.

Then the ordering $\preceq$ is a **partial ordering** on $S$ if and only if $\preceq$ is not connected.

That is, if and only if $\struct {S, \preceq}$ has at least one pair which is non-comparable:

- $\exists x, y \in S: x \npreceq y \land y \npreceq x$

## Also defined as

Some sources define a **partial ordering** to be the structure known on $\mathsf{Pr} \infty \mathsf{fWiki}$ as an ordering, that is, whose nature (**partial** or total) is unspecified.

## Also known as

A **partial ordering** as defined here is sometimes referred to as a **weak partial ordering**, to distinguish it from a strict partial ordering

## Also see

## Sources

- 1968: A.N. Kolmogorov and S.V. Fomin:
*Introductory Real Analysis*... (previous) ... (next): $\S 3.3$: Ordered sets. Order types - 1982: P.M. Cohn:
*Algebra Volume 1*(2nd ed.) ... (previous) ... (next): Chapter $1$: Sets and mappings: $\S 1.5$: Ordered Sets - 1983: George F. Simmons:
*Introduction to Topology and Modern Analysis*... (previous) ... (next): $\S 1$: Sets and Set Inclusion