Definitions of reciprocal:

• noun:   something (a term or expression or concept) that has a reciprocal relation to something else

  Example: "Risk is the reciprocal of safety"

• noun:   hybridization involving a pair of crosses that reverse the sexes associated with each genotype
• noun:   (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
• adjective:   concerning each of two or more persons or things; especially given or done in return

  Example: "Reciprocal aid"

• adjective:   of or relating to the multiplicative inverse of a quantity or function

  Example: "The reciprocal ratio of a:b is b:a"

• adjective:   of or relating to or suggestive of complementation