What is the inverse of resistance?

Resistance measures how much a material opposes the flow of electric current. The inverse (or reciprocal) of this property describes how easily a material allows current to flow, which is known as conductance. Conductance is mathematically represented as G = 1/R and is measured in Siemens (formerly 'mhos', which is 'ohm' spelled backwards). The other options refer to different physics concepts. Reactance is the opposition to AC current caused by capacitance or inductance. Permeability and reluctance are properties related to magnetic circuits, not the direct inverse of electrical resistance.