reciprocity

A reciprocal condition or relationship.

A mutual or cooperative interchange of favors or privileges, especially the exchange of rights or privileges of trade between nations.

Reciprocal action or relation; free interchange; mutual responsiveness in act or effect.

Equality of commercial privileges between the subjects of different, governments in each other's ports, with respect to shipping or merchandise, to the extent established by treaty.

In the Kantian philosophy, mutual action and reaction in the strict, mechanical sense.