läbipaisuv

Läbipaisuv is an Estonian adjective used to describe the property of a material or medium that allows passage through it. It covers both permeability of liquids and gases in fields such as hydrology, soil science, and membrane technology, and the transmission of light in optics and textiles. The degree of läbipaisvus can vary from nearly impermeable to highly permeable, and depends on factors such as porosity, pore size, and thickness.

For fluids, permeability is often described with coefficients (hydraulic or gas permeability) and diffusion measures. In optics and photography, transmittance or optical clarity defines how much light passes through. In textiles and building materials, terms like semi-permeable or breathable indicate selective passage of water vapor or air.

Common examples include porous rock or soil allowing water to drain; filtration membranes that pass solvents while blocking larger particles; and breathable fabrics or membrane-based building envelopes that permit moisture transfer while preventing liquid water ingress.

Origin and usage: The term is of Estonian origin, formed from through (läbi) and a root related to passing or permeation. It is used in specialized contexts and may be translated differently across disciplines (permeable, translucent, or breathable, depending on the focus).