Signs and Symbols, what's the difference?

A sign is an entity that indicates (represents) another entity to an agent (a human, animal or robot) for some purpose. It enters as a correlative in the relation of signification and significance (meaning for constructs) causing something else to come to the mind as its effects. According to the classic views of Aristotle, Augustine, and Aquinas, 'signification is a relationship between two sorts of things, which are signs and the kinds of things they signify'. To express a significance, the signs may both point out and stand for the entities signified, or just take the place and substitute as the symbols do. Also, signs or symbols may signify only mental constructs or they signify both constructs and external things. Then, since the signs signify (express, denote, connote, or designate) but the constructs mean, the significance of a sign in a language (natural or formal) equals the meaning of the mental construct designated by the sign.

A symbol, in its basic sense, is a conventional representation of a concept; i.e., an idea, object, quality, quantity, etc. In more psychological and philosophical terms, all concepts are symbolic in nature, and representations for these concepts are simply token artifacts that are allegorical to (but do not directly codify) a symbolic meaning, or symbolism. From the most general systemics perspective, a symbol is a communication mean, it is a graphical, written, vocal or other physical object which, usually in a syntetic sense, is used to the representation of another, more complex, physical or abstract object, or an object property. It is also used in various metaphoric notions.