I have been thinking about the Japanese notion of Aida (written as 間，あいだ）. Aida literally has two meanings: one is a spatial gap between two things, and the other is a certain time interval between two events. The conceptual basis that is common in those two usages might be the "betweenness."
Aida seems to be a very practical notion to describe interpersonal relations. Aida is a spatial distance between two (or more) people such as personal space. Aida is also a temporal interval that happens in verbal communications between two (or more) people. If I can share an appropriate Aida with another person, I may have a meaningful communication, or at least, I may have the sense that we have something in common.
Consider, for example, an appropriate spatial distance with another person. If it is too far, there would be no communication between you and that person. If it is too near, there would be a certain communication but it becomes awkward and unnatural, unless you are familiar with that person. Aida itself is invisible and empty but it is the grounding condition which makes possible the interpersonal communication. Aida is relevant to the interpersonal coordination too.
.....Writing all this reminded me of the Japanese phenomenological psychiatrist, Bin Kimura. He has left a lot of writings on the notion of Aida. I am going to read them again!