Merriam Webster dictionary

reciprocity

noun rec·i·proc·i·ty \ˌre-sə-ˈprä-s(ə-)tē\

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: a situation or relationship in which two people or groups agree to do something similar for each other, to allow each other to have the same rights, etc. : a reciprocal arrangement or relationshi

plural rec·i·proc·i·ties

1: the quality or state of being reciprocal : mutual dependence, action, or influence
2: a mutual exchange of privileges; specifically : a recognition by one of two countries or institutions of the validity of licenses or privileges granted by the other

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Grownups know that little things matter … and that relationships are based on respect and reciprocity. —Margaret Carlson, Time, 4 June 2001
Introduced in the McKinley Tariff of 1890, reciprocity gave the president authority to remove items from the free list if their countries of origin placed unreasonable tariffs on American goods. —Mary Beth Norton et al., A People and a Nation, 1988
Indeed when they talked on an indifferent subject, as now, there was ever a second silent conversation passing between their emotions, so perfect was the reciprocity between them. —Thomas Hardy, Jude the Obscure, 1895
The proposal calls for reciprocity in trade relations.

(see ¹reciprocal)
First Known Use: 1766