0 a number that is part of a series in which each number is the sum (= total when added together) of the two numbers that come before it in the series, for example 0, 1, 1, 2, 3, 5, 8 ..: --
Changes in trends very often correspond with Fibonacci numbers.
The fruit of a pineapple is arranged in two interlocking helices, eight in one direction, thirteen in the other, each being a Fibonacci number.
What was curious was that the Fibonacci numbers cropped up all over the place in the botanical world - for instance, when you count the numbers of petals on flowers, or the spirals in which the seeds arrange themselves in the flower-head.
The progressions of Fibonacci numbers are commonly found in the growth rates and structures of nature.