Anisotropy

Part of speech: noun

Definitions

1. The property of having different physical characteristics or values depending on the direction in which they are measured
2. the quality of exhibiting variation in physical properties when measured along different spatial axes or directions
3. a characteristic wherein material behavior or measurable attributes differ based on the orientation or direction of observation

Etymology: Anisotropy is a compound built from two Greek-derived parts. The prefix "an-" is a negating element, "not", and "isotropy" is itself formed from "iso-" (equal) and Greek "tropos" (turn, direction), so the whole word means something like "not equal in every direction." The word was therefore constructed from classical building blocks rather than inherited from ancient usage, and it describes a property that the ancient Greeks had no reason to name. The key idea sits in the second half. Isotropy names the condition of being the same in all directions, and "an-" simply reverses it. A material is anisotropic when, say, wood splits more easily along the grain than across it, or when light travels at different speeds depending on the direction it passes through a crystal. The word thus describes a contrast with an ideal of uniformity rather than a thing that exists on its own.