preorder
reflexive and transitive binary relation
equivalence relation
reflexive, symmetric and transitive relation
partial order
reflexive antisymmetric transitive binary relation
reflexive transitive closure
operation on binary relations
hierarchy
preorder defined on a set
well-quasi-ordering
preorder in which every infinite sequence has an increasing or equivalent pair of consecutive values
weak ordering
generalization of total orderings allowing ties, axiomatized as strict weak orders, total preorders, or ordered partitions
specialization (pre)order
preorder on the set of the points of a topological space
subsequence
binary relation between sequences (strings)