What does porous mean?
Porous describes a substance containing many tiny pores or interconnected openings. Such openings may allow air, water, gases, or other fluids to pass through, making porous materials useful in filtration, insulation, construction, and agriculture. The word is also associated with materials that absorb liquids readily, although porosity and permeability are technically related rather than identical concepts. Porous materials include porous soil, porous membranes, porous stone, and porous fabrics. In everyday descriptions, “porous” may suggest that a surface is unable to keep out water or air completely: porous brick can absorb moisture, while porous clothing allows heat and perspiration to escape. The term is standard in both British and American English and appears regularly in technical writing, environmental discussion, and descriptions of buildings and materials. Its contrasting term is “impermeable,” meaning unable to allow passage through.
adjectiveFull of pores or tiny openings, allowing air, liquids, or gases to pass through. Porous materials can absorb fluids and admit air more readily than nonporous ones.
- Containing pores or tiny interconnected openings through which air, liquids, or gases can pass.
- Permeable enough for fluids or gases to move through, often because of such openings.
"The porous stone allowed rainwater to seep slowly through the wall."
"The porous membrane filters the solution while allowing the solvent to pass through."
"Heavy rain can make the porous soil erode more quickly."
A porous material is full of holes; a permeable material lets fluids pass through.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does porous come from?
The adjective comes from Latin porosus, meaning “full of pores,” formed from porus, “pore” or “opening.” Latin porus was borrowed from Greek poros, meaning “passage” or “way.” English later developed related forms such as pore, porosity, and porously, all belonging to the same word family.
Related word forms
How porous is actually used
The word is neutral in register and is common in scientific, technical, environmental, and architectural contexts. It is especially common before nouns such as “material,” “membrane,” “soil,” and “surface.”
Easily confused with porous
Porous describes a material containing pores or openings, whereas permeable describes something that allows fluids or gases to pass through.