izotropia

Isotropia, also written isotropia in some languages, is commonly referred to in English as isotropy. It denotes the property of being the same in all directions, reflecting directional independence of a given quantity. Isotropy is contrasted with anisotropy, where properties vary with direction. The term can apply to materials, fields, or spaces, and is related to, but distinct from, homogeneity, which concerns uniformity across space rather than direction.

In physics, spatial isotropy implies there is no preferred direction in space; the laws of nature have the same form under rotation. The cosmological principle uses isotropy (and homogeneity) to describe the large-scale structure of the universe. Observations of the cosmic microwave background show overall isotropy with small anisotropies that seed structure formation.

In optics, an isotropic medium has a refractive index that is the same for light propagating in any direction. Gases and many liquids are approximately isotropic, while many crystalline solids are anisotropic and can exhibit birefringence.

In materials science, isotropic materials have mechanical properties that are direction-independent, such as stiffness and strength in a given orientation. This is an idealization for most real materials, which may be anisotropic due to internal structure or texture. Polymers, glasses, and some metals can often be treated as isotropic in certain conditions.