We define a sign as a physical thing or event whose function is to indicate some other thing or event. The meaning of a sign may be inherent in its physical form and its context, as in the case of the height of a column of mercury in a thermometer as an indica- tion of temperature, or the return of robins in the spring. Or, the meaning of a sign may be merely identified with its physical form as in the case of a hurricane signal or a quarantine flag. But in either case, the meaning of the sign may be ascertained by sensory means. The fact that a thing may be both a symbol (in one context) and a sign (in another context) has led to confusion and misunderstanding. (White 1949:27)
WHITE, Leslie. 1949. The science of culture: a study of man and civilization. New York: Grove Press.