Symbol

https://en.wikipedia.org/wiki/Symbol

A symbol is a thing (mark, sign, pointer, cue) used to convey meaning by representing something apart from itself.

• Icon, index and symbol are means to represent entities. An icon resambles the entity it represents; index is a pointer to the entity it represents; a symbol has got nothing in common with the entity it represents, it is a completelly arbitrary relation so it must be learned in order to be understood.

• Symbols usually dwell in the visual and auditory domain expressed as words, images, gestures, sounds, or some other form; they may take any form or the form of anything they encounter and in that regard they are a lot like polymimetic alloys. If it is hard to tell apart an actual thing from its (possible and plausible) symbol, then fugazi. Communication, human or otherwise, possibly even the process of thinking, is achieved through the use of symbols.

• Numerals are symbols for numbers. Alphabetic letters may be symbols for sounds. Personal names are symbols representing individuals. A variable x may symbolize anything at all.

• The word symbol derives from the Greek σύμβολον meaning "token, watchword"; from σύν (together) and βάλλω (put, throw).