Definition/Meaning  Word/Phrase 
oral sex, reciprocal 
69
,
sixtynine

material's capacity to conduct electricity; measured as the reciprocal of electrical resistance 
conductance

reciprocal relation between two or more things 
correlation
,
correlativity

relationship, reciprocal 
correlation
,
mutuality
,
reciprocity

unit of elastance equal to the reciprocal of a farad 
daraf

unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists 
diopter
,
dioptre

reciprocal of capacitance 
elastance
,
elastance unit
,
electrical elastance

reciprocal transfer of equivalent sums of money especially the currencies of different countries 
exchange
,
interchange

reciprocal group action 
getting even
,
paying back
,
return

mean of n numbers expressed as the reciprocal of the arithmetic mean of the reciprocals of the numbers 
harmonic mean

(cosmology) the ratio of the speed of recession of a galaxy (due to the expansion of the universe) to its distance from the observer; the reciprocal of the Hubble constant is the age of the universe 
Hubble's constant
,
Hubble constant

mutual or reciprocal action; interacting 
interaction

reciprocal relation between interdependent entities (objects or individuals or groups) 
interdependence
,
interdependency
,
mutuality

reciprocal action and reaction 
interplay

reciprocal reflection between two reflecting surfaces 
interreflection

mutual or reciprocal relation or relatedness 
interrelatedness
,
interrelation
,
interrelationship

unit of conductance equal to the reciprocal of an ohm 
mho
,
reciprocal ohm
,
S
,
siemens

(mathematics) one of a pair of numbers whose product is 1: the reciprocal of 2/3 is 3/2; the multiplicative inverse of 7 is 1/7 
multiplicative inverse
,
reciprocal

(from potential of Hydrogen) the logarithm of the reciprocal of hydrogenion concentration in gram atoms per liter; provides a measure on a scale from 0 to 14 of the acidity or alkalinity of a solution (where 7 is neutral and greater than 7 is more basic 
pH
,
pH scale

radius of the circle of curvature; the absolute value of the reciprocal of the curvature of a curve at a given point 
radius of curvature
