Order Relations
There are a number of mathematical concepts which act to define some semblance of an “order” on a set. I organize these concepts here and collectively refer to them as ordering relations.
Formally, I require an ordering relation to be a binary relation which is at least reflexive and transitive. (I.e., at least a preorder.)
Diagram of order relations with arrows in direction of strength / subsumation (⊇):
┌► directed set ──┐
preorder ─┤ ├► upper semilattice ──► lattice ──► linear order
└► partial order ─┘
(Incidentlaly, the relation underlying this diagram is a partial order and a directed set but not a semilattice)
Characterization table:
Examples are from me, Mason Mackaman (thanks!), and online. Some may be incorrect.
Viewed as graphs,
Graph conditions corresponding to the other relations have no good names as far as I know.