What does conductance mean?
Conductance is the measure of how easily something — most commonly electric current, but also heat or ions — passes through a material or component. It is formally defined in electronics as the reciprocal of resistance: where resistance impedes the flow of current, conductance quantifies how freely it flows. The SI unit of electrical conductance is the siemens (S), though engineers once used the playful 'mho', the word 'ohm' reversed. Because conductance increases as resistance falls, the two concepts describe the same underlying behaviour from opposite directions, which makes conductance especially convenient when analysing circuits connected in parallel, where conductances simply add together. Beyond electronics, the term appears in thermodynamics as thermal conductance and in physiology, where neuroscientists speak of membrane conductance to describe how readily ions cross a cell's surface. Precise and technical in register, conductance is essential vocabulary for physics, engineering, and the life sciences.
nounThe degree to which an object or material conducts electricity, defined as the reciprocal of electrical resistance and measured in siemens. More generally, the property of transmitting heat or a fluid.
- The readiness of a component or substance to conduct electricity; the reciprocal of resistance, measured in siemens (formerly mhos).
- The ability of a material or structure to transmit heat (thermal conductance).
- In physiology, the ease with which ions cross a cell membrane (e.g. membrane conductance in neuroscience).
"The sensor measures the conductance of the solution to determine its salt concentration."
"Because the two resistors are wired in parallel, their combined conductance is simply the sum of their individual conductances."
"Rising stomatal conductance allowed the leaf to exchange more carbon dioxide with the air."
Plural form appears chiefly in technical contexts, e.g. summing the conductances of parallel circuit elements.
"When resistors are connected in parallel, their individual conductances add directly."
Conductance is simply resistance turned upside down — literally its mathematical reciprocal — so a circuit that resists less, conducts more.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of conductance
Conductance derives from the Latin verb 'ducere' ('to lead'), via 'conduct-', the past-participial stem of 'conducere' meaning 'to bring together or lead'. The English noun was formed from 'conduct' with the noun-forming suffix '-ance' during the development of modern scientific vocabulary in the nineteenth century, as physicists sought precise terms for measurable electrical properties. It shares this Latin root with related words such as 'conductor', 'conduction', and 'conductivity'.
Related word forms
How conductance is actually used
Conductance is a technical term used chiefly in physics, electrical engineering, chemistry, and physiology; it is rare in everyday speech. Its SI unit is the siemens (symbol S), named for Werner von Siemens; the older unit, the 'mho' ('ohm' spelled backwards), survives mainly as informal or historical usage. In casual writing, 'conductivity' is often loosely substituted for 'conductance', though they are technically distinct.
Easily confused with conductance
Conductance is a property of a specific object or sample (measured in siemens), whereas conductivity is an intrinsic material property independent of dimensions (measured in siemens per metre).
Conduction is the process by which heat or electricity is transmitted through a material, while conductance is the measure of how readily that transmission occurs.