Hasse diagram in the context of "Order theory"

In logic, a logical connective (also called a logical operator, sentential connective, or sentential operator) is an operator that combines or modifies one or more logical variables or formulas, similarly to how arithmetic connectives like ${\displaystyle +}$ and ${\displaystyle -}$ combine or negate arithmetic expressions. For instance, in the syntax of propositional logic, the binary connective ${\displaystyle \lor }$ (meaning "or") can be used to join the two logical formulas ${\displaystyle P}$ and ${\displaystyle Q}$, producing the complex formula ${\displaystyle P\lor Q}$.

Unlike in algebra, there are many symbols in use for each logical connective. The table "Logical connectives" shows examples.

In mathematics, especially order theory, the covering relation of a partially ordered set is the binary relation which holds between comparable elements that are immediate neighbours. The covering relation is commonly used to graphically express the partial order by means of the Hasse diagram.

In mathematics, especially in order theory, the greatest element of a subset ${\displaystyle S}$ of a partially ordered set (poset) is an element of ${\displaystyle S}$ that is greater than every other element of ${\displaystyle S}$. The term least element is defined dually, that is, it is an element of ${\displaystyle S}$ that is smaller than every other element of ${\displaystyle S.}$

In mathematics, especially in order theory, a maximal element of a subset ${\displaystyle S}$ of some preordered set is an element of ${\displaystyle S}$ that is not smaller than any other element in ${\displaystyle S}$. A minimal element of a subset ${\displaystyle S}$ of some preordered set is defined dually as an element of ${\displaystyle S}$ that is not greater than any other element in ${\displaystyle S}$.

The notions of maximal and minimal elements are weaker than those of greatest element and least element which are also known, respectively, as maximum and minimum. The maximum of a subset ${\displaystyle S}$ of a preordered set is an element of ${\displaystyle S}$ which is greater than or equal to any other element of ${\displaystyle S,}$ and the minimum of ${\displaystyle S}$ is again defined dually. In the particular case of a partially ordered set, while there can be at most one maximum and at most one minimum there may be multiple maximal or minimal elements. Specializing further to totally ordered sets, the notions of maximal element and maximum coincide, and the notions of minimal element and minimum coincide.

In mathematics, an abstract polytope is an algebraic partially ordered set which captures certain combinatorial properties of a traditional polytope without specifying purely geometric properties such as the position of vertices.

A geometric polytope is said to be a realization of an abstract polytope in some real n-dimensional space, typically Euclidean. This abstract definition allows more general combinatorial structures than traditional definitions of a polytope, thus allowing new objects that have no counterpart in traditional theory.