reciprocation

US /rɪˌsɪp.rəˈkeɪ.ʃən/
UK /rɪˌsɪp.rəˈkeɪ.ʃən/
1.

sự đáp lại

the fact of feeling or behaving toward someone else in the same way as they feel or behave toward you:

:
Our relationship is based upon reciprocation.