Many important spatial patterns of Nature are either irregular or fragmented to such an extreme degree that ... classical geometry ... is hardly of any help in describing their form. ... I hope to show that it is possible in many cases to remedy this absence of geometric representation by using a family of shapes I propose to call fractals -- or fractal sets. [Mandelbrot, "Fractals," 1977]来自PIE*bhreg, 分开，破开，词源同break, fragment, fraction. 用于数学名词。