Sign: Something that stands for something else. Most theorists distinguish between the icon and the index. An icon signifies what it represents by its likeness or similarity to that object, person, place, and so on. The cave paintings at Lascaux, France, for instance, are icons representing a variety of animals. An index is directly and regularly connected, physically or through a cause-effect relationship, to what it signifies. Clouds darkening the sky could thus be an index for an approaching thunderstorm, as smoke is for fire. In works such as “On a New List of Categories” (1867), American philosopher Charles Sanders Peirce contended that symbols are also signs. Calling the symbol a “sign proper,” he argued that symbols do not involve natural or inherent relationships to what they suggest but, rather, arbitrary socially and culturally determined relationships. For instance, when flown by ships, monochromatic flags of certain colors are internationally understood to represent specific conditions; red signifies danger or revolution, yellow quarantine, black death or protest, white truce or surrender, green proceed, and orange distress.
Swiss linguist Ferdinand de Saussure defined the “linguistic sign” as composed of a signifier, a linguistic “sound-image” used to represent some comparatively abstract concept, and a signified, the concept being represented. As set forth in the Cours de linguistique générale (Course in General Linguistics), published posthumously in 1916 and based on student notes of his lectures, Saussure argued that a “linguistic sign is not a link between a thing and a name, but between a concept and a sound pattern,” and characterized a “linguistic system” as “a series of differences of sound combined with a series of differences of ideas.” He also argued that the relationship between signifier and signified is arbitrary, that is, that no intrinsic or natural relationship exists between them. For instance, French speakers regard the signifier pour as meaning “for,” whereas to English speakers the same signifier means “cause to flow in a continuous stream” or “rain heavily.” Saussure further argued that the meaning of any given sign arises from the difference between it and other signs in the same linguistic system.
Differences in language make meanings recognizable; the word pour means what it does in English because it is distinct from other words (such as four and peer) with which it can be compared and contrasted. Differences in meaning — including differences in the meaning of a given word in different verbal contexts — are learned conventions that speakers understand as if they were positive qualities, givens of Nature.