What does anisotropic mean in materials?

• A. Properties are identical in all directions
• B. Properties vary with crystallographic orientation
• C. Properties depend on temperature only
• D. Properties depend on grain size

Answer: (B)

Anisotropic means a material's properties depend on the direction you measure them. This happens because the internal structure, especially in crystals, has specific directions defined by the arrangement of atoms and bonds, so stiffness, conductivity, refractive index, and other properties can vary with crystallographic orientation. A single crystal will show different values along different axes, while a polycrystalline material with randomly oriented grains can appear isotropic at macroscopic scales unless there’s texture or alignment. The other statements describe isotropy or attribute variation to temperature or grain size, which are separate ideas from directional dependence.