a relation of mutual dependence or action or influence
"The success of our two companies relies on reciprocity, as we both provide essential services that neither could offer alone."
mutual exchange of commercial or other privileges
"The two nations signed a new treaty to establish reciprocity, allowing citizens of each country to work and trade without additional visas or tariffs."
The characteristic of being reciprocal, e.g. of a relationship between people.
"Their friendship was built on reciprocity, where every time she lent him money or offered advice, he returned the favor in kind without hesitation."