Capacity of a rock or soil material to transmit a fluid.

The overall ability of water to flow through a geologic material, accounting for all openings in the material (e.g., between grains, through fractures, along lava tubes). For HRS purposes, the terms hydraulic conductivity and permeability are used interchangeably.

A measure of fabric porosity or openness, expressed in cubic feet of air per minute per square foot of fabric at a 0.5" w.c. Pressure differential.

Abaility of a coating film to allow the passage or penetration of a liquid or gas.

the ability of a membrane to allow substances to pass through it.

The ability of water (or other fluid) to move through a rock.

The measure of the ability of a material to act as a path for magnetic lines of force.

the permeation rate divided by the pressure gradient of the gas or vapor. For a homogeneous material that obeys Fick's law, the permeability is equal to the product of the diffusion coefficient and the solubility coefficient of the gas or vapor.

The ability of a formation to transmit groundwater or other fluids through pores and cracks.

( Ped .). The rate at which water moves through a soil under a standard pressure gradient. Usually defined as the amount of water traversing 1 sq. cm. of soil surface under a pressure gradient of one dyne per cm. ( BCFT ). Cf . Infiltration capacity.

The degree to which a material allows fluids to pass through it via an interconnected network of pores and cracks.

the ability of a material, such as soil, to permit liquids or gases to pass through, usually through pores or openings

The ease with which dissolved materials can cross a membrane; if the membrane is freely permeable, any molecule can cross it; if impermeable, nothing can cross; most biological membranes are selectively permeable.

the ability of molecules to pass through the cell membrane.

the ease with which water passes through a bulk mass of soil or a layer of soil. In the Map Unit Interpretation Record (MUIR) database, permeability is expressed as the number of inches per hour that water moves downward through the saturated soil.

The process whereby a fluid or gas passes through a barrier at the molecular level. Passage of these materials through defects such as holes or tears does not constitute permeability.

the capacity of a rock (coal) to transmit a fluid

Degree to which underground rock and soil pores are interconnected and thus a measure of the degree to which water can flow freely from one pore to another. Compare porosity.

A measure of how well a material can carry magnetic flux. Air is considered as having unity (one) permeability. All other materials have a permeability in excess of one.

governs the rate at which water moves through a soil. Sands and gravels have very high permeability, heavy clays very low.

(1) The property of a material that permits appreciable movement of water through it when it is saturated and the movement is actuated by hydrostatic pressure of the magnitude normally encountered in natural subsurface water. Perviousness is sometimes used in the same sense as permeability. (2) The ability of natural and artificial materials to transmit fluids.

A term used to describe the ability of water to move through a porus medium (such as soil). Soil with a high coefficient (value) of permability can transmit water more quickly than soil with a low coefficient of permability.

Measure of the magnetic characteristics of a material. A measure of the effect of a nearby magnet on a material.

The ability of a substrate to allow a solution to pass through it.

Ability of a cake or medium to pass liquids; or the rate of flow to fluid under a differential pressure through a material. Air permeability measurement provides a convenient comparison for various media and indicates the construction requirements for specific particle size retention. As a rule of thumb, lower permeability values indicate finer particle retentivity.

The rate of flow of water through soils.

The property of permitting liquids or gases to pass through. A highly permeable soil, such as sand, allows a liquid to pass through quickly. Clay has a low permeability.

A measure of the ease with which a fluid such as water or oil moves through a rock when the pores are connected. Geologists express permeability in a unit named the darcy, but oilmen use the millidarcy because most of the rocks they come in contact with are not very permeable.

The property of bulk material ( SAND, crushed rock, soft rock in situ) which permit movement of water through its pores.

Capable of transmitting water (porous rock, sediment, or soil); the rate at which water moves through rocks or soil.

Leakiness; ability to be penetrated.

The ability of an aquifer or water-bearing formation to allow water to pass through it. Permeability is also known as effective porosity because it is a function of interconnected saturated pore spaces.

A measure of how well a material can transmit water. Materials such as gravel, that transmit water quickly, have high values of permeability. Materials such as shale, that transmit water poorly, have low values. Permeability is primarily determined by the size of the pore spaces and their degree of interconnection. Permeability measures are expressed in units of velocity, such as centimeters per second, and assume a gradient of one vertical foot of drop per linear foot.

the rate at which water moves down through the subsoil

The ease with which water can pass through a layer of soil or rock. Permeability depends upon particle size and the shape or packing of grains and is expressed a rate of discharge per unit area.

Absolute permeability. A measure of the ability of a rock to conduct a fluid through its interconnected pores when that fluid is at 100% saturation. Measured in darcies or millidarcies. See also effective permeability.

The capacity of a rock for transmitting a fluid; a measure of the relative ease with which a porous medium can transmit a liquid.

The ease with which a fluid flows through a porous material (wood) in response to pressure.

the degree to which groundwater can move freely through an aquifer measured by the interconnection of pores and fractures

Penetrability.

n: 1. a measure of the ease with which a fluid flows through the connecting pore spaces of a formation or cement. The unit of measurement is the millidarcy. 2. fluid conductivity of a porous medium. 3. ability of a fluid to flow within the interconnected pore network of a porous medium.

Permeability is a measure of the ease with which fluid flows through a porous medium under the influence of a pressure gradient and/or gravity. Permeability is, in most situations, essentially independent of pressure, temperature, and concentration and depends only on the nature of the porous medium. SUTRA simulations are formulated in terms of permeability (rather than hydraulic conductivity). The effective permeability at any point in the system can depend on the direction of ground-water flow. See Section 2.2 of the SUTRA documentation for details.

a measure of the rate of water movement through soil or other substance.

The property of porous materials indicating the ease with which liquids or gases will be transmitted through a soil or other porous material. Permeabilities are not affected by changing the type of liquid.

The ease with which a magnetic flux can be established in a given magnetic circuit.

Ratio between flux density, B, and magnetizing force, H. Permeability describes the intrinsic willingness of a material to conduct magnetic flux lines.(Course Material/EddyCurrents/Introduction/historyofET.htm)

The quality that enables the soil to transmit water or air, measured as the number of inches per hour that water moves through the soil. Terms describing permeability are very slow (less than 0.06 inch), slow (0.06 to 0.20 inch), moderately slow (0.2 to 0.6 inch), moderate (0.6 to 2.0 inches), moderately rapid (2.0 to 6.0 inches), rapid (6.0 to 20 inches), and very rapid (more than 20 inches). pH value.

the ease with which water passes through the ground

(1) Magnetic permeability, the ratio of the magnetic induction to the intensity of the magnetizing field. (2) In a mould, the porosity of foundry sands and the ability of trapped gases to escape through the sand.

The ease or difficulty with which water will flow or pass through the pores of soil or rock.

The quality that enables soil or rock to transmit water. Sedimentary: Rock formed by precipitation from water or from depositions of gravel, sand, silt and clay.

the ability of water to penetrate the cement.

the property or capacity for transmitting a fluid. Permeability is measured as the number of inches per hour that water moves downward through the saturated soil. Terms describing permeability are: Very slow . = 0.06 in/hr; Slow = 0.06 to 0.2 in/hr; Moderately slow = 0.2 to 0.6 in/hr; Moderate = 0.6 to 2.0 in/hr; Moderately rapid = 2 to 6 in/hr; Rapid = 6 to 20 in/hr; and Very Rapid = 20 in/hr. Plant available water capacity - the capacity of soils to hold water available for use by most plants.

Pertaining to a rock or soil and its capacity for transmitting a fluid through its pore spaces.

A measure of the ability of a rock to transmit fluid through pore spaces.

The rate at which a gas (such as methyl bromide) flows through a material (such as a fumigation sheet).

Ability of water to penetrate and move through soil downward to the groundwater, or laterally through soil towards surface water. The permeability rate for soil is the speed at which water will penetrate and move in a given amount of time. For storage ponds, the rate of 1 foot per year or less is desirable.

The capacity of a geologic formation to allow water or natural gas to pass through it.

The capability of a given substance to allow the passage of a fluid. Permeability depends on the size of and the degree of connection among a substance's pores.

The rate at which liquids pass through soil or other materials in a specified direction.

Diffusion of a vapor or fluid through a porous body without physically affecting it.

The time rate of water vapor transmission through unit area of a material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions.

The measure of the ability of porous material to transmit fluid.

The capacity of a porous rock, sediment, or soil for transmitting a fluid; a measure of the relative ease of fluid flow under unequal pressure.

the property of something that can be pervaded by a liquid (as by osmosis or diffusion)

The measurable capacity through which a rock formation allows fluid to flow. Permeability and porosity are the two most important characteristics of reservoir rock.

A measure of the ability of a porous medium to transmit fluids under a hydraulic gradient.

The ease with which gases, liquids (water), or plant roots penetrate or pass through a bulk mass of soil or a layer of soil. Since different soil horizons vary in permeability, the particular horizon under question should be designated.

Describes the ability of rock or soil to transmit water.

A soil characteristic that enables water or air to move through the profile, measured as the number of inches per hour that water moves down ward through the saturated soil. The rate at which water moves through the least permeable layer governs soil permeability.

The property of rock or soil that permits water to pass by flowing through interconnected voids (spaces). Permeable bedrock makes a good aquifer, a rock layer that yields water to wells.

The ability of a medium to pass a fluid under pressure.

the quality of soil that permits water and air to be moved through it.

the property of soil or rock which allows the passage of water through it.

The ability of small molecules to diffuse slowly through a polymeric membrane.

The ability of water (or other fluid) to flow through a soil by traveling through the void spaces. A high permeability indicates flow will occur rapidly, and vice versa.

ability of a material to transmit water. Permeability determines its ability to yield water.

The ability of a material, usually a vapor, to pass through a film.

Permeability is the property of a material, i.e. the degree to which it allows permeation to occur.

The quality of a soil horizon that enables water or air to move through it. Terms used to describe permeability are as follows: very slow, slow, moderately slow, moderate, moderately rapid, rapid, and very rapid.

the property of a substance that allows lines of magnetic force to pass through it. (A permeable substance does not diminish magnetic fields.)

The measure of a formation's ability to transmit fluids and/or gases.

the property or capacity of a soil or rock for transmitting a fluid, usually water; the rate at which a fluid can move through a medium

A physical constant that reflects a material or medium's relative "ease" or "difficulty" conducting or "shunting" magnetic fields.

This represents the affinity a core material has for concentrating a magnetic field generated by current flow into flux. It is in effect the gain of the core material. In the CGS (Centimeter-Gram-Second) system of units the permeability of air, which is pretty much the same as free space, is normalized to 1. The permeability of core materials is a multiplier of free space. A common permeability of high quality power ferrites is 2000-5000. For high grade silicon steel the permeability can exceed 50,000.

Ability of liquid to flow through rock, groundwater, soil, or other substance.

The capacity of an aggregate particle, or group of particles, to transmit a fluid.

the capacity of a porouos material to transmit fluids. Permeability is a function of the sizes, shapes, and degree of connection among pore spaces, the viscosity of the fluid, and the pressure driving the fluid.

The rate at which a liquid or gas under pressure passes through a solid material by diffusion and solution. In rubber terminology, it is the rate of gas flow expressed in atmospheric cubic centimeters per second through an Elastomeric material one centimeter square and one centimeter thick. (atm cc/cm squared / cm/sec)

The capacity of a rock for transmitting a fluid. Permeability depends on size and shape of pores in the rock, along with the size, shape, and extent of the connections between pore spaces.

The ratio of the magnetic induction of a material to the magnetizing force producing it (B/H). Pole - An area where the lines of magnetic flux are concentrated.

the degree or rate at which a liquid will pass through rock or other earth material.

A measure of how much better a material is as a path for magnetic flux as compared to free space. The symbol for permeability is "µ". For free space, µ = 1.

The measurable capacity of a rock to allow a fluid to flow through it. Along with porosity, it is one of the two most critical properties of the reservoir rock. To be commercially producible, oil or gas must be able to flow from the reservoir rock into the well.

The voids in a soil or aquifer media that allows passage of water through the media at a measured rate.

The capability of soil or other geologic formations to transmit water.

A measure of how quickly soil allows water to flow through it.

The rate at which water passes through the soil, usually measured in a laboratory.

A measure of the resistance offered by rock to the movement of fluids through it.

A characteristic of porosity of a material generally listed as the rate of diffusion of a pressurized gas through a material. The pore structure of some materials allows them to absorb or adsorb more moisture than other materials. Limestones are generally more permeable than granites.

a function of grain size diameter, used to describe the ease at which water penetrates the soil surface.

Defines the ability of a rock or sediment to transmit fluid.

the rate at which water or other liquids pass through the connected pore spaces of a material

A property of material that indicates how much magnetization occurs when a magnetic field is applied.

The ratio of the magnetic induction of a material to the magnetizing force producing it (B/H). NOTE: The permeability of air is 1.

Ability to be permeated by gases or liquids; a measure of the freedom with which gases or liquids can diffuse through a material.

A qualitative description of the relative ease with which rock, soil, or sediment will transmit a fluid (liquid or gas). Often used as a synonym for hydraulic conductivity or coefficient of permeability.

Ability of rock to transmit fluids through pore spaces.

Compare? The ease with which water, or other fluid, passes through a substance.

is the rate of diffusion through a porous material.

A property measured as the rate of passage of a liquid or gas through a compact; measured under specified conditions.

The capacity of a substance (for example, soil or rock) to allow water to pass through it. Sand, for example, is said to have high permeability.

the degree to which soils and rock are interconnected, depends upon size and shape of pores; size and shape of interconnections and their extent List of Glossary Terms

The ability of a rock or other material to allow water to flow through its interconnected spaces. Permeable bedrock makes a good aquifer, a rock layer that yields water to wells. See porosity. (3 MB porosity animation available)

The capacity of a reservoir rock to transmit fluids.

The extent to which a material acts as an effective barrier to water permeation through absorption.

A measure of the relative ease with which water will move through soil or rock.

Material constant characterising gas penetration, like water vapour, oxygen or carbondioxide.

the ability of a water bearing material to transmit water. It is measured by the quantity of water passing through a unit cross section, in a unit time, under 100 percent hydraulic gradient.

the quality of something that allows water or another substance to flow through it. if water flows through soil quickly, the soil is highly permeable.

In our case, the ease with which water can penetrate through a substance. Solid rock has zero permeability. Sand has a high permeability.

A measurement of the ability of air to flow through a filter at a given differential pressure. The value is expressed as (U.S.) cubic feet per minute at .5" water gauge differential or (Metric) liter/min at 20mm water gauge differential.

The measure of how much better a material is than air as a path for magnetic lines of force. Air is assumed to have a permeability of 1.

The ability of a porous medium suchas soil to transmit fluids or gases.

The quality of soil that allows air or water to move through it.

The speed with which gasses (and liquids) can pass through a self-adhesive film. The amount of printing on an adhesive film also effects the film's permeability; the more printing ink coverage on a piece of film, the less permeable the film will be. See Outgas.

A measure of a material’s ability to transmit water.

In general, the ratio of the changes in magnetic induction to changes in magnetizing force (B to H) is called the permeability.

The mold–metal property which allows passage of mold/core gasses during the pouring of molten metal.

A characteristic of soil which allows water to flow through it because of gravity.

The measure of gas or liquid leakage through a material or hermetic barrier. Refers both to the potential for leakage in the sealing technology as well as the other materials (shells, contacts, etc.) used in the fabrication of the part.

The degree to which fluids such as oil, gas and water can move through the pore spaces of a reservoir rock.

The passage or diffusion of a gas, vapor, liquid or solid through a barrier without physically or chemically affecting it.

Ability of a membrane or other material to permit a substance to pass through it. www.cartech.doe.gov/resources/glossary.html

The quality of permitting passage of water through openings without causing rupture or displacement.

capability of a material to let pass other molecules or particles

(mu) - tendency of a substance to concentrate magnetic field mu = B/H.

The capacity of rock or soil to transmit water.

the capacity or ability of a porous rock, sediment, or soil to allow the movement of water through its pores

The ability of geologic material to transmit water. In this report, the term is used in the same sense as "hydraulic conductivity." See: hydraulic conductivity

Capacity of a porous rock formation to allow fluid to flow within the interconnecting pore network.

The rate at which a liquid or gas can penetrate into or through a flexible polyurethane foam. Usually associated with airflow, a measure of the openness of the foam.

a measure of the ease with which a fluid can pass through the pore spaces of a formation. Learn More.

The property of a filter medium that permits a fluid to pass through under a pressure differential.

A measure of the rate at which water can percolate through soil.

the ability of a textile to allow air or water vapour to pass through it.

The ability of a fluid substance to pass through a material. Filters have varying degrees of permeability that allow substances of different sizes to pass through them.

the quality or condition of allowing passage of liquids or gases through a layer. Q R SAE: the abbreviation for the Society of Automotive Engineers.

see magnetic permeability.

The degree to which a body of rock will permit a fluid to flow through it. It is a function of the shape of the capillary pore spaces and the degree to which pores are connected.

(1) The capacity of a porous material to conduct or transmit fluids. (2) The amount of a fluid moving through a barrier in a unit time, unit area, and unit pressure gradient not normalized for but directly related to the thickness.

A measure of the ease with which water penetrates a material.

The quality or condition of allowing passage of liquids or gasses through a rubber layer.

A property measured as a rate of passage of a liquid or gas through a coating

Property of allowing passage of fluids.

Capacity of a soil or other surface to be penetrated by water sinking into the ground under the force of gravity. It thus expresses the rate of percolation.

µ) - The ratio of the magnetic induction of a material to the magnetizing force producing it (B/H). The magnetic permeability of a vacuum (µo) is 4π×10-7 N/Amp2.

In relation to ground-water, refers to the ability of soil or rock to transmit water.

The relationship of flow per unit area to differential pressure across a filter medium.

The degree to which a membrane or coating film will allow the passage or penetration of a liquid or gas. Adding flake to a coating enhances its permeability rating.

The rate of flow of a liquid or gas through a porous material.

The property of a formation which quantifies the flow of a fluid through the pore spaces and into the wellbore.

the ability of a material to allow a liquid to pass through it. Permeable materials, such as gravel and sand, allow water to move quickly through them.

Ability of a surface or coating of paper to allow passage of a gas, liquid or vapour

Measured in the laboratory, the rate of water movement through a soil column under saturated conditions, usually expressed as k in calculations per specific ASTM or AASHTO tests, and typically expressed in inches per hour or meters per second. See ASTM D 2434. Compare to Infiltration.

The property of a porous rock or soil to transmit a fluid without impairment of the medium. Measure of relative ease of flow under unequal pressure.

The capacity of a soil or groundwater aquifer to transmit water.

The  property  of  soils  which  permits  the  passage  of  any  fluid.    Permeability depends on grain size, void ratio, shape and arrangement of pores.

the measure of how quickly and easily water flows through materials such as soil or rocks.

a measure of a porous material's ability to allow fluids or gases to flow through its pores. An important property of rocks that determines how much and how rapidly fluids or gases can move through them; for example, how much water can be pumped from an aquifer (see: porosity).

the ability of a material to allow the passage of a liquid, such as water through rocks. Permeable materials, such as gravel and sand, allow water to move quickly through them, whereas unpermeable material, such as clay, don't allow water to flow freely.

The measure of the capacity for transmitting a fluid through a substance.

A measure of water vapor transmission. The ability of a substrate to resist transfer of water vapor from one side to the other.

Expressed in cubic feet per minute (CFM), the resistance to flow through a media. The lower the perm number, the greater the resistance. The permeability of a filter media is a quality control measure for cartridge and D.E. filter materials.

To permit passage of gas through the molecular structure of a given material.

Ability of a material to allow water to pass through.

The quality of the soil that enables water to move downward through the profile.

A measure of the ease with which a fluid can flow through a porous medium. It depends on the physical properties of the medium, for example grain size, porosity and pore shape.

capacity of soil or other geologic formation to transmit water. pumping lift distance water must be lifted in a well from the pumping level to the ground surface.

Ability of a material to allow another material to pass through it without rupture.

The property of a mold material to allow passage of mold/core gases during the pouring of molten metal.

A measure of a materials ability to support the existence of magnetic lines of flux. It is a ratio of flux density in gauss, (ß), to a magnetizing force, (H), in oersteds. The permeability of air is considered as unity (1).

A measure of the ease with which air, roots and water penetrate the soil.

Permeability is a measure of how readily liquids can pass through a soil. Silt loams and sandy loam soils are relatively permeable. An impermeable soil is one which does not allow liquids to pass through easily. Clay loams and loams are relatively impermeable. Manure storages should be located over IMPERMEABLE soils so that seepage will not pass down through the soil into the groundwater.

a measure of the capacity of rock or stratum to allow water or other fluids such as oil to pass through it.

Permeability is a physical property of soil and rock. It is a measure of how easily a fluid, such as water, air, or liquid waste, moves through a porous rock or sand and gravel deposit. Two primary factors that contribute to permeability are the size of voids and their interconnectedness.

The property of a material that allows a resists a substance to pass or flow through it; the rate of such passage.

A measure of fabric porosity or openness, usually expressed in cfm at a 0.5" H20 pressure differential.

The qualitative estimate of the ease with which fluids, gases, or plant roots pass through soil.

The ease with which gases, liquids, or plant roots penetrate or pass through the soil or a layer of soil. Permeability is determined by soil texture, structure, and porosity.

(1) The passage by diffusion (or rate of passage) of a gas, vapour, liquid, or solid through a barrier without physically or chemically affecting it. (2) The ability of a material to carry magnetism, compared to air, which has a permeability of 1.

A measure of the resistance of a porous medium to the flow of fluids. Permeability is a reinforcement property, independent of the resin.

(1) Ability of a material (generally an earth material) to transmit fluids (water) through its pores when subjected to pressure or a difference in head. Expressed in units of volume of fluid (water) per unit time per cross section area of material for a given hydraulic head; (2) description of the ease with which a fluid may move through a porous medium; abbreviation of intrinsic permeability. It is a property of the porous medium only, in contrast to hydraulic conductivity, which is a property of both the porous medium and the fluid content of the medium.

A term used to describe the ability of water or other liquid to move through a porous formation under the action of a gradient. The facility with which a fluid will move through a formation is greater for some than for others. For a given bed, the permeability is expressed by a constant K representing the flow through unit in unit time under the influence of a unit gradient. The flow is expressed in terms of entire water.

The rate at which water passes through a material.

The property which allows the flow of water through a soil. See also coefficient of permeability.

Rate of gas flow through a solid material, under pressure. Expressed in atmospheric cubic centimeters per second through an elastomeric material one centimeter square and one centimeter thick (atm cc/cm2/cm/sec).

1. The ability of a body, such as a reverse osmosis or ultrafiltration membrane, to pass a liquid under pressure or to pass ions under the influence of an electric current as an ion exchange membrane in electrodialysis.

(n) The ease of a liquid to enter and spread to every part of an object

The measure of ease with which a magnetic field can be established in a material.

A term used to express the ability of a substance, such as iron or steel, to carry magnetic lines of force.

Measure of how m how much better a material is as a path for magnetic lines of force with respect to air which has a permeability of one. Symbolized by the Greek lower case letter mu ().

A property of a porous medium: a measure of the capacity of the medium to transmit fluids. The common unit of mesurement of the millidarcy.

The degree to which a fluid will pass through a permeable substance under specified conditions. The space or void volume between molecules allowing fluid flow.

The ease with which air, or plant roots penetrate into or pass through a specific horizon.

The degree to which an interface such as a cell membrane or epithelium allows the passage of a substance across it.

A rock is said to be permeable if water, oil or gas can easily flow when a pressure gradient is applied. Permeability in the rock is controlled by a relationship between grain size, clay content and distribution and poreblocking quartz cement.

The portion of the hydraulic conductivity of a porous medium that is dependent on the pore structure only: where is hydraulic conductivity, is permeability, is density, μ is dynamic viscosity, and is acceleration of gravity.

The capacity of a substance, such as rock, to transmit a fluid. The degree of permeability depends on the number, size, and shape of the pores and/or fractures in the rock and their interconnections. It is measured by the time it takes a fluid of standard viscosity to move a given distance. The unit of permeability is the Darcy.

A measure of the ability of soil, sediments, and rock to transport water horizontally and vertically. Permeability is dependent on the porosity of the medium the water is flowing through. Some rocks like granite have very poor permeability, while rocks like shale are actually quite pervious. As for soil, sand is the most pervious, while clay has the lowest permeability. Silt is usually somewhere in the middle.

The rate of diffusion or the ability of liquid to flow through a certain material.

The property of a mold material to allow passage of gases. The property in sand molds which permits the passage of gases.

In electromagnetism, permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. Magnetic permeability is represented by the Greek letter μ. This term was coined in September, 1885 by Oliver Heaviside.

In the earth sciences, permeability (commonly symbolized as κ, or k) is a measure of the ability of a material (typically, a rock or unconsolidated material) to transmit fluids. It is of great importance in determining the flow characteristics of hydrocarbons in oil and gas reservoirs, and of groundwater in aquifers.