reciprocity
noun
Definitions
The characteristic of being reciprocal, e.g. of a relationship between people.
Example: In a friendship, reciprocity occurs where the contribution of each party meets the expectations of the other party.
A reciprocal relationship.
A relation of mutual dependence or action or influence.
(grammar) A reciprocal construction involves two noun phrases where each of the participants occupies both the role of agent and patient with respect to the other. see: Wikipedia:Reciprocal pronoun.