reciprocity

Definitions:

Reciprocal obligation or right; equal rights or benefits to be mutually yielded or enjoyed.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
Free interchange of action or relation; commercial relationship between two nations by which each grants the other equal and similar advantages not enjoyed by other nations; as, a treaty of reciprocity between the United States and Canada.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
Interchange; equal mutual rights or benefits to be yielded or enjoyed; mutual action and reaction.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
Mutual obligations: action and reaction.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (noun) (n.) (noun)
State of being reciprocal; mutuality.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)

Usage examples:

The next step was to carry out the promises of reciprocity with the United States.
- The Canadian Commonwealth by Agnes C. Laut
This reciprocity of infinitude forms their life.
- Seraphita by Honore de Balzac
Must there not be a reciprocity of service to make friendship lasting?
- The Memorabilia Recollections of Socrates by Xenophon