(Can we clean up(+) this sense?) A representation, a thing serving to represent something (as to an interpreting mind). It is a representation in the sense of something which represents, as opposed to its operation or relation of representing, and also as opposed to a process or activity of representing, which produces it. (The produced representamen can itself seem or be a process or activity, for example a song or a theatrical performance, or a rock's tumbling in an informative way, or a logical argument).
circa 1897: Charles Sanders Peirce [aut.] and Justus Buchler [ed.], Philosophical Writings of Peirce, chapter 7: “Logic as Semiotic: The Theory of Signs”, § 1: “What is a Sign? Three Divisions of Logic”, page 99 (from a circa 1897 manuscript (CP 2.227–9), first published in the 1940 selection The Philosophy of Peirce: Selected Writings, and later reprinted sic in 1955 by Dover Publications, Inc., New York; ISBN 0486202178, 9780486202174)
A sign, or representamen, is something which stands to somebody for something in some respect or capacity.
(Can we find and add a quotation of William Hamilton to this entry?)
"I confine the word representation to the operation of a sign or its relation to the object for the interpreter of the representation. The concrete subject that represents I call a sign or a representamen." — C. S. Peirce, Lowell Lectures 1903, Collected Papers of Charles Sanders Peirce, v. 1, paragraph 540. Eprint.
"Possibly there may be Representamens that are not Signs." — C. S. Peirce, "A Syllabus of Certain Topics of Logic", 1903, the Essential Peirce v. 2, pp. 272-3. Eprint.
"It is the science of what is quasi-necessarily true of the representamina of any scientific intelligence in order that they may hold good of any object, that is, may be true." — C. S. Peirce, Collected Papers v. 2, paragraph 229. Eprint.
Four instances of "representamina" used by John Deely, Four Ages of Understanding (2001, U of Toronto Press), p. 726, Google Books limited preview Eprint