Symbols are objects, characters, or other concrete representations of ideas, concepts, or other abstractions. For example, in the United States and Canada, a red octagon is a symbol for the traffic sign meaning "STOP". In more psychological and philosophical terms, every perception is symbolic, and humans often react to symbolism on a subconscious level.
Common examples of symbols are the symbols used on maps to denote places of interest, such as crossed sabers to indicate a battlefield, and the numerals used to represent numbers. Common psychological symbols are the use of a gun to represent a penis or a tunnel to represent a vagina. See: phallic symbol and yonic symbol.