Umberto Eco quotes - page 11
What is a symbol? Etymologically speaking, the word σύμβολον comes from σνμβάλλω, to throw-with, to make something coincide with something else: a symbol was originally an identification mark made up of two halves of a coin or of a medal. Two halves of the same thing, either one standing for the other, both becoming, however, fully effective only when they matched to make up, again, the original whole. ... in the original concept of symbol, there is the suggestion of a final recomposition. Etymologies, however, do not necessarily tell the truth - or, at least, they tell the truth, in terms of historical, not of structural, semantics. What is frequently appreciated in many so-called symbols is exactly their vagueness, their openness, their fruitful ineffectiveness to express a 'final' meaning, so that with symbols and by symbols one indicates what is always beyond one's reach.
Umberto Eco