Generally, the term adjunction refers to attachment or affixing to another. Something attached as a dependent or auxiliary part. For example, a branch agency is an adjunct of the main department or Administrative Agency.
In civil law, adjunction is the permanent union of a thing belonging to one person to something that belongs to someone else. It takes place when a thing belonging to one person is attached or united to that which belongs to another, whether this union is caused by inclusion. For instance, one man's diamond encased in another's ring by soldering or by building a house on another's land.