Definition of preorders:
(v) :
(transitive) To order (goods or services) in advance, before they are available.
(n) :
An order for goods or services placed in advance.
(v) :
(transitive) To sort or arrange beforehand.
(adj) :
(computing theory, of a traversal of a tree) Such that, recursively, the root is visited before the left and right subtrees.
(n) :
(set theory, order theory) A binary relation that is reflexive and transitive.