"Adjacent" is to "adjacency" as "contains" is to what?
An adjacency relation is one which denotes whether two objects are adjacent.
The two neighbors are adjacent, and hence have an adjacency relation.
What is the equivalent for a "contains" relation, for example:
The box contains oranges, and hence they have a ??? relationship.
I am not sure whether "containment" is appropriate given its connotations.
Note that the word may not necessarily be based on "contains", perhaps on a synonym.
Solution 1:
There seems to be some reluctance to sanction the use of 'containment' in a spatial sense.
Mukergee and Sarkar have no such qualms in their article Grounded Acquisition of Containment Prepositions :
... Here we demonstrate that it is possible for a purely perceptual system to form notions of containment, well recognised as one of the earliest spatial concepts arising around the age of six months (Casasola et al, 2003)....
And neither do Lockwood et al in Automatic Classification of Containment and Support Spatial Relations in English and Dutch:
... For example, in English containment relationships are categorised as 'in' and support relationships are classified as 'on'....
Solution 2:
There are two ways to answer the question.
First (the serious answer) consider how relationships are named in scholarly discourse in the topic. An influential paper on topological relationships in natural language semantics includes the following passage:
Most approaches to spatial language have assumed that the simplest spatial notions are (after Piaget) topological and universal (containment, contiguity, proximity, support, represented as semantic primitives such as IN, ON, UNDER, etc.)
If scholars who discuss containment relationships use the term containment, you could hardly be considered silly for doing the same.
Second (the facetious answer). Adjacent takes its nominal form from the paradigm for the Latin source word from which it ultimately derives. The present active neuter participle for Latin adjacere 'lie beside' is adjacentia 'lying beside'. Contain ultimately derives from Latin continere 'hold together'. Its present active neuter participle is continentia 'holding together'. So the word you are looking for is continence. But even in Latin continentia could refer to self-restraint and chastity. Medical use of the term in English dates to the early 20th century (though incontinent is attested in the 18th century).
Solution 3:
I'm not sure that the "containment" question can be correlated to adjacency. Adjacency is a mutual relationship, both parties are adjacent to the other. The oranges will never contain the box. The box will always be the dominant party in this example, thereby fulfilling the requirement of restricting growth, if you will. I like "container-contained", but it does sound a little too textbook for conversational use. The cop-out answer of "There isn't an answer" is looking better and better.