Cohesion

Cohesion is the quality of connectedness within a group of entities. The more cohesive this group, the more meaningful and enduring their connection to each other and the harder for them to separate.

In the context of systems, it is the chief property of them all, without which they can't be called one.

While not all elements of a system are necessarily in constant interaction to the same degree, the less they are, the less cohesion there is and without any cohesion a system will disagregate and cease to exist, leaving only the dispersed elements in its place.

These non-interacting elements form the horizon of systems, whereas the center of most intense interaction form its locus of interaction.