reciprocity

The characteristic of being reciprocal, e.g. of a relationship between people.

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.

(international law) The mutual exchange of rights, privileges or obligations between nations. see: Wikipedia:Reciprocity (international relations).

(psychology) The responses of individuals to the actions of others.