# Lattice-complemented subgroup

This article defines a subgroup property: a property that can be evaluated to true/false given a group and a subgroup thereof, invariant under subgroup equivalence. View a complete list of subgroup properties[SHOW MORE]

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## Definition

### Symbol-free definition

A subgroup of a group is said to be lattice-complemented if there is another subgroup such that:

• The two subgroups intersect trivially
• The join of the two subgroups is the whole group

### Definition with symbols

A subgroup $H$ of a group $G$ is said to be lattice-complemented if there is another subgroup $K$ such that:

• $H\cap K$ is trivial
• $\langle H,K \rangle = G$

## Formalisms

BEWARE! This section of the article uses terminology local to the wiki, possibly without giving a full explanation of the terminology used (though efforts have been made to clarify terminology as much as possible within the particular context)

This subgroup property is a monadic second-order subgroup property, viz., it has a monadic second-order description in the theory of groups
View other monadic second-order subgroup properties

## Metaproperties

### Transitivity

NO: This subgroup property is not transitive: a subgroup with this property in a subgroup with this property, need not have the property in the whole group
ABOUT THIS PROPERTY: View variations of this property that are transitive|View variations of this property that are not transitive
ABOUT TRANSITIVITY: View a complete list of subgroup properties that are not transitive|View facts related to transitivity of subgroup properties | View a survey article on disproving transitivity

A lattice-complemented subgroup of a lattice-complemented subgroup need not be lattice-complemented. Further information: Lattice-complemented is not transitive

### Trimness

This subgroup property is trim -- it is both trivially true (true for the trivial subgroup) and identity-true (true for a group as a subgroup of itself).
View other trim subgroup properties | View other trivially true subgroup properties | View other identity-true subgroup properties

### Intermediate subgroup condition

NO: This subgroup property does not satisfy the intermediate subgroup condition: it is possible to have a subgroup satisfying the property in the whole group but not satisfying the property in some intermediate subgroup.
ABOUT THIS PROPERTY: View variations of this property satisfying intermediate subgroup condition | View variations of this property not satisfying intermediate subgroup condition
ABOUT INTERMEDIATE SUBGROUP CONDITION: View other subgroup properties not satisfying intermediate subgroup condition| View facts about intermediate subgroup condition

If $H$ is a lattice-complemented subgroup of a group $G$, and $H \le L \le G$, $H$ is not necessarily lattice-complemented in $L$. For full proof, refer: Lattice-complemented does not satisfy intermediate subgroup condition