involving two people or groups who agree to help each other or behave in the same way to each other (Oxford)
A reciprocal action or arrangement involves two people or groups of people who behave in the same way or agree to help each other and give each other advantages . Cambridge)
Anita had a reciprocal arrangement with her brother—each would take care of the other’s children if the need arose. (Oxford)
The two colleges have a reciprocal arrangement whereby students from one college can attend classes at the other.(Oxford)
a reciprocal basis.
reciprocal arrangement
Mutual
Common
Unanswered
Unreciprocated
Direct
Reciprocally
Reciprocal