Indexicality
In linguistics and adjacent fields, "indexicality" refers to the positioning of some object or person into a communication-relevant context.
Maybe the simplest example of this type of indexing is the establishment of self or current location into a conversation.
Having indexed oneself as the entity currently speaking—a common implication across all known, natural (not intentionally invented) languages—one can thus say "I" or "my" or "this" and have it be understand that what's being referenced is the person speaking, something belonging to the person speaking, or something being pointed or otherwise gestured at by the person speaking.
You might also index the location in which one is having a conversation as "here" or a person being discussed as "him," which then allows for contextual referencing of that location or person from that point forward (or until reindexing occurs).
A whole subclass of terms (called "deictics") allow us to use indexed concepts to rapidly communicate within a commonly understood context.
Saying something will happen "tomorrow" implies a shared understanding of what "today" is, while talking about something "over there" suggests that the people having the conversation share a common understanding of where "here" is—in the literal, geographic sense, or in the metaphorical sense.
This concept extends beyond linguistics into semiotics (the study of signs and symbols and their use), as well.
Pointing at someone or something can index that person or object into the collective contextual understanding, and pointing one's chin toward a sunrise may index the sun, the horizon, or the concept of "morning."
This is an interesting, often invisible realm of exploration, in part because most of us utilize communication indexes all day long without realizing it, but also because it opens up the possibility of all sorts of misunderstandings if we inadvertently leave someone (or a group of someones) out of a seemingly intuitive and shared cultural index, or if we build relationships (and accompanying dynamics) around indexes that seem clear, but which are (unbeknownst to us) communicating different things to different people.
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