What does anisotropy mean?
Anisotropy is the property of exhibiting different values of a physical characteristic when measured along different directions. A material that is anisotropic might be strong along one axis but weak along another, conduct heat well in one orientation but poorly in another, or transmit light unevenly depending on its path through the substance. Familiar examples include wood, which splits readily along the grain, layered rocks, liquid crystals, and many engineered composites such as carbon fibre. The word is the direct counterpart of isotropy, which denotes complete uniformity in all directions. Anisotropy is central to materials science, crystallography, geophysics — where seismic waves reveal directional structure deep within the Earth — and cosmology, where minute anisotropies in the cosmic microwave background carry information about the early universe. Because it is a technical term, it appears almost exclusively in scientific writing rather than everyday conversation, yet it names a phenomenon with wide practical consequences for how we design, build, and interpret the physical world.
nounThe property of a material or medium of having different physical properties in different directions, such that measurements like strength, conductivity, or light transmission vary depending on the direction in which they are taken.
- The directional dependence of a material's physical properties (mechanical, thermal, electrical, optical, or magnetic).
- In cosmology and physics more broadly, any observed variation of a quantity with direction, such as anisotropy in the cosmic microwave background.
"The anisotropy of wood explains why it splits easily along the grain but resists splitting across it."
"Because of seismic anisotropy, earthquake waves travel at different speeds through the mantle depending on their direction."
"Engineers must account for the anisotropy of carbon-fibre composites when designing aircraft components."
The plural is standard in scientific literature, especially when referring to multiple measured variations, such as anisotropies in the cosmic microwave background.
"Satellite maps of temperature anisotropies across the sky transformed modern cosmology."
Wood, crystals, and even the fabric of the early universe all share one secret: they behave differently depending on which way you push them.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of anisotropy
Anisotropy derives from Greek roots: 'an-' meaning 'not' or 'without', 'isos' meaning 'equal', and 'tropos' meaning 'turn' or 'way', giving the sense of properties that do not turn equally in every direction. The term was formed on the model of the earlier word isotropy, which described uniformity in all directions. It entered scientific English during the nineteenth century as physicists and crystallographers formalised the study of direction-dependent properties in crystals and other media. Its sibling terms isotropy and isotropic share the same Greek ancestry.
Related word forms
How anisotropy is actually used
A technical term used chiefly in physics, materials science, geology, and engineering; rarely encountered in everyday speech. It carries no emotional connotation and is neutral in register, though always formal or scientific.
Easily confused with anisotropy
Isotropy is the opposite property — uniformity of physical properties in all directions — whereas anisotropy describes properties that vary with direction.