• Rel(S, T) (relations)
• s ≺ t
• ≺^T
• mapping
• ≺(s)
• Rel(S) (relations)
• ≺∣_T
• (=_S)
• reflexive
• connex
• symmetric
• antisymmetric
• transitive
• preorder
• partial order
• total order
• ≺-lower bound
• ≺-upper bound
• ⪯-least element
• ⪯-greatest element
• well-order
• equivalence relation
• S∕∼
• ≪
• ∠
• Closures
• Heterogenous equality