A recording of an event produced by a connection between an object and its role in the event. In semiotics, as presented by Charles Sanders Peirce (American pragmatist, 1839-1914; pr. purse), there are three kinds of signs: icon, index and symbol. Whether a sign belongs in one category or another is dependent upon the nature of its relationship between the sign itself (which Peirce called the referent) and its the actual meaning. An icon is a meaning which is based upon similarity or appearance (for example, similarity in shape). According to Pierce, icons are "the only means of directly communicating an idea." An index is a meaning based upon some cause and effect relationship: "Because the indexical sign is understood to be connected to the real object, it is capable of making that object conceptually present."The plural form of this word is indices. The adjectival form is indexical.Examples of indices: Thermometers carry a certain meaning because of variation in temperature.