Pinnate

Pinnate refers to feather-like or multi-divided features arising from both sides of a common axis. In biological morphology the term applies to plant or animal structures, but it also is used in other disciplines, for example in describing crystalline structures such as some forms of ice or metal crystals, and in earth sciences, where it may refer to patterns of erosion or stream beds.

The term derives from the Latin word pinna meaning "feather", "wing", or "fin". A similar term is pectinate, which refers to a comb-like arrangement of parts (arising from one side of an axis only). The term "pinnate" is used largely in contrast to palmate, in which the parts or structures radiate out from a common point. The term pennate is cognate with "pinnate" and is variously used, but there is no consistent difference in the meaning or usage of the two words.