INDEX

An index is a dynamic and/or spatial connection between the object and the interpreter of the index sign. Indices do not necessarily resemble their objects.

Indices, as Pierce put it, "set direct attention to their objects by blind compulsion." Indices call attention. When the sign's interpreter is exposed to the index, attention is routed to the object. For example, a cab driver's shout will call attention to the availability of his cab. Indices also refer to a single and specific object or object set. The pronouns "that" or "this" are indices to the noun to follow in the sentence, as in "That flock of birds."

Subindexes are a subcategory of indices defining signs actually connected to an object. A formal name, a letter attached to a diagram, and a footnote number are examples of subindexes.