reciprocal
adjective /rɪˈsɪprəkl/
  /rɪˈsɪprəkl/
- involving two people or groups who agree to help each other or behave in the same way to each other
- The two colleges have a reciprocal arrangement whereby students from one college can attend classes at the other.
 - a reciprocal relationship between citizens and the state
 - Anita had a reciprocal arrangement with her brother—each would take care of the other’s children if the need arose.
 
Oxford Collocations DictionaryReciprocal is used with these nouns:- arrangement
 - exchange
 - relationship
 - …
 
Word Originlate 16th cent.: from Latin reciprocus (based on re- ‘back’ + pro- ‘forward’) + -al.