Pinnation
Type of spatial arrangement / From Wikipedia, the free encyclopedia
Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals,[1] such as some forms of ice or metal crystals,[2][3] and in patterns of erosion or stream beds.[4]
The term derives from the Latin word pinna meaning "feather", "wing", or "fin". A similar concept is "pectination", which is a comb-like arrangement of parts (arising from one side of an axis only). Pinnation is commonly referred to in contrast to "palmation", in which the parts or structures radiate out from a common point. The terms "pinnation" and "pennation" are cognate, and although they are sometimes used distinctly, there is no consistent difference in the meaning or usage of the two words.[5][6]