A symbol is a person or a concept that represents, stands for or suggests another idea, visual image, belief, action or material entity. Symbols take the form of words, sounds, gestures, ideas or visual images and are used to convey other ideas and beliefs. For example, a red octagon may be a symbol for "STOP". On a map, a blue line might represent a river. Numerals are symbols for numbers. Alphabetic letters may be symbols for sounds. Personal names are symbols representing individuals. A red rose may symbolize love and compassion. The variable x in a mathematical equation may symbolize the position of a particle in space.

The at-sign, @, normally read aloud as "at", also commonly called the at symbol or commercial at, and less commonly a wide range of other terms (such as the strudel), is originally an accounting and commercial invoice abbreviation meaning "at a rate of" (e.g. 7 widgets @ £2 = £14). It was not included on the keyboard of the earliest commercially successful typewriters, but was on at least one 1889 model and the very successful Underwood models from the "Underwood No. 5" in 1900 onward. It is now universally included on computer keyboards. The mark is encoded at .