Order theory is a branch of mathematics that studies various kinds of objects (often binary relations) that capture the intuitive notion of ordering, providing a framework for saying when one thing is "less than" or "precedes" another.
An alphabetical list of many notions of order theory can be found in the order theory glossary. See also inequality, extreme value and mathematical optimization.
Overview edit
Distinguished elements of partial orders edit
- Greatest element (maximum, top, unit), Least element (minimum, bottom, zero)
- Maximal element, minimal element
- Upper bound
- Least upper bound (supremum, join)
- Greatest lower bound (infimum, meet)
- Limit superior and limit inferior
- Irreducible element
- Prime element
- Compact element
Subsets of partial orders edit
- Cofinal and coinitial set, sometimes also called dense
- Meet-dense set and join-dense set
- Linked set (upwards and downwards)
- Directed set (upwards and downwards)
- centered and σ-centered set
- Net (mathematics)
- Upper set and lower set
- Ideal and filter
Special types of partial orders edit
- Completeness (order theory)
- Dense order
- Distributivity (order theory)
- Ascending chain condition
- Countable chain condition, often abbreviated as ccc
- Knaster's condition, sometimes denoted property (K)
Well-orders edit
Completeness properties edit
- Semilattice
- Lattice
- (Directed) complete partial order, (d)cpo
- Bounded complete
- Complete lattice
- Infinite divisibility
Orders with further algebraic operations edit
- Heyting algebra
- Complete Heyting algebra
- MV-algebra
- Ockham algebras:
- Orthocomplemented lattice
- Quantale
Orders in algebra edit
Functions between partial orders edit
- Monotonic
- Pointwise order of functions
- Galois connection
- Order embedding
- Order isomorphism
- Closure operator
- Functions that preserve suprema/infima
Completions and free constructions edit
Domain theory edit
Orders in mathematical logic edit
Orders in topology edit
- Stone duality
- Specialization (pre)order
- Order topology of a total order (open interval topology)
- Alexandrov topology
- Upper topology
- Scott topology
- Lawson topology
- Finer topology