The Commens Dictionary
Quote from ‘Syllabus: Syllabus of a course of Lectures at the Lowell Institute beginning 1903, Nov. 23. On Some Topics of Logic’
Subindices or hyposemes are signs which are rendered such principally by an actual connection with their objects. Thus a proper name, [a] personal demonstrative, or relative pronoun or the letter attached to a diagram, denotes what it does owing to a real connection with its object but none of these is an Index, since it is not an individual.