Infinity symbol in bookbinding to indicate that a book is printed on acid-free paper and will therefore be long-lasting. In modern mysticism, the infinity symbol has become identified with a variation of the ouroboros, an ancient image of a snake eating its own tail that has also come to symbolize the infinite, and the ouroboros is sometimes drawn in figure-eight form to reflect this identification, rather than in its more traditional circular form. In the works of Vladimir Nabokov, including "The Gift" and "Pale Fire", the figure-eight shape is used symbolically to refer to the Möbius strip and the infinite, for instance
Prime (symbol) to subscripts – "x"′ generally means something related to or derived from "x". For example, if a point is represented by the Cartesian coordinates , then that point rotated, translated or reflected might be represented as . The prime symbol is not related to prime numbers. Usually, the meaning of "x"′ is defined when it is first used, but sometimes its meaning is assumed to be understood: The prime is said to "decorate" the letter to which it applies. The same convention is adopted in functional programming, particularly in Haskell. In geometry, geography and astronomy, prime and double prime are