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.
Related word: reciprocally
reciprocal
noun[ C ]uk/rɪˈsɪp.rə.kəl/us/rɪˈsɪp.rə.kəl/
（数学）倒数
a number that, when multiplied by another number, results in 1