A number sequence discovered by a thirteenth century Italian mathematician Leonardo Fibonacci (ca 1170-1250), who introduced Arabic numbers to Europe, in which the sum of any two consecutive numbers equals the next highest number – i.e., following this sequence: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55 and so on. The ratio of any number to its next highest number approaches 0.618 after the first four numbers. Fibonacci numbers are said to be based upon observations of the Great Pyramid of Gizeh in Egypt by Fibonacci. These numbers are used by technical analysts to determine price objectives from percentage retracements. See also: Fibonacci retracements, Fibonacci arcs, Fibonacci fans, and Fibonacci time zones.

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