The reciprocal of their friendship was evident in their mutual support.
Взаимность их дружбы была очевидна в их взаимной поддержке.
Definitions
A mathematical expression or function so related to another that their product is one; the quantity obtained by dividing the number one by a given quantity.
The reciprocal of 5 is 1/5.
A counterpart or equivalent in a different context or system.
Each clause in the contract has a reciprocal to balance the obligations.