# Partially ordered set

## Mathematical set with an ordering / From Wikipedia, the free encyclopedia

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In mathematics, especially order theory, a **partial order** on a set is an arrangement such that, for certain pairs of elements, one precedes the other. The word *partial* is used to indicate that not every pair of elements needs to be comparable; that is, there may be pairs for which neither element precedes the other. Partial orders thus generalize total orders, in which every pair is comparable. Formally, a partial order is a homogeneous binary relation that is reflexive, transitive and antisymmetric. A **partially ordered set** (**poset** for short) is a set on which a partial order is defined.

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indicates that the column's property is always true the row's term (at the very left), while ✗ indicates that the property is not guaranteed in general (it might, or might not, hold). For example, that every equivalence relation is symmetric, but not necessarily antisymmetric, is indicated by in the "Symmetric" column and ✗ in the "Antisymmetric" column, respectively. All definitions tacitly require the homogeneous relation be transitive: for all if and then |