Y 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 Y in the "Symmetric" column and ✗ in the "Antisymmetric" column, respectively.
All definitions tacitly require the homogeneous relation be transitive: for all if and then
A term's definition may require additional properties that are not listed in this table.
A weak order on the set where is ranked below and and are of equal rank, and is ranked above and I) representation as a strict weak order where is shown as an arrow from to ; II) representation as a total preorder shown using arrows; III) representation as an ordered partition, with the sets of the partition as dotted ellipses and the total order on these sets shown with arrows.The 13 possible strict weak orderings on a set of three elements The only total orders are shown in black. Two orderings are connected by an edge if they differ by a single dichotomy.
There are several common ways of formalizing weak orderings, that are different from each other but cryptomorphic (interconvertable with no loss of information): they may be axiomatized as strict weak orderings (strictly partially ordered sets in which incomparability is a transitive relation), as total preorders (transitive binary relations in which at least one of the two possible relations exists between every pair of elements), or as ordered partitions (partitions of the elements into disjoint subsets, together with a total order on the subsets). In many cases another representation called a preferential arrangement based on a utility function is also possible.