Editing Glossary of order theory (section)

== H ==

* '''[[Heyting algebra]]'''. A Heyting algebra ''H'' is a bounded lattice in which the function ''f''<sub>''a''</sub>: ''H'' → ''H'', given by ''f''<sub>''a''</sub>(''x'') = ''a'' &and; ''x'' is the lower adjoint of a [[Galois connection]], for every element ''a'' of ''H''. The upper adjoint of ''f''<sub>''a''</sub> is then denoted by ''g''<sub>''a''</sub>, with ''g''<sub>''a''</sub>(''x'') = ''a'' ⇒; ''x''. Every [[Boolean algebra (structure)|Boolean algebra]] is a Heyting algebra.
* '''[[Hasse diagram]]'''. A Hasse diagram is a type of mathematical diagram used to represent a finite partially ordered set, in the form of a drawing of its [[transitive reduction]].
* '''[[Homogeneous relation]]'''. A [[homogeneous relation]] on a set <math>X</math> is a subset of <math>X \times X.</math> Said differently, it is a [[binary relation]] over <math>X</math> and itself.