preorder
noun
Definitions
An order for goods or services placed in advance.
A binary relation that is reflexive and transitive.
Example: The relation of logical implication over sentences is an example of a preorder.
verb
Definitions
To order (goods or services) in advance, before they are available.
To sort or arrange beforehand.
adjective
Definitions
(of a traversal of a tree) Such that, recursively, the root is visited before the left and right subtrees.