decussation

When two things cross and form the shape of an X, that's decussation. Nature has many examples of decussation, from patterns in leaves to nerve fibers in the human body.

Decussation is a technical term for something that happens all the time in the natural world. In our brains, for example, there is a type of decussation where nerve fibers cross from one hemisphere to the other. Botanists describe the decussation of leaves on a plant when they cross each other in patterns that form right angles. The Latin source is decussis, "the figure or shape of ten," or in Roman numerals, X.

Definitions of decussation

1. noun

   an intersection or crossing of two tracts in the form of the letter X
   synonyms: chiasm, chiasma

   types:

   chiasma opticum, optic chiasm, optic chiasma

   the crossing of the optic nerves from the two eyes at the base of the brain

   type of:

   anatomical structure, bodily structure, body structure, complex body part, structure

   a particular complex anatomical part of a living thing