Reciprocally /(rē̇*sĭp"rō̇*kal*ly̆)/

Re·cip·ro·cal·ly

Reciprocally

adv.
  1. In a reciprocal manner; so that each affects the other, and is equally affected by it; interchangeably; mutually.
    These two particles do reciprocally affect each other with the same force.
  2. In the manner of reciprocals. (Math.)

Phrases & Compounds
Reciprocally proportional
proportional, as two variable quantities, so that the one shall have a constant ratio to the reciprocal of the other.