rec·i·proc·i·ty
noun/ˌresɪˈprɒsəti/
/ˌresɪˈprɑːsəti/
[uncountable] (formal)- a situation in which two people, countries, etc. provide the same help or advantages to each other
互惠；互助；互换 Word Originmid 18th cent.: from French réciprocité, from réciproque, from Latin reciprocus ‘moving backwards and forwards’ (based on re- ‘back’ + pro- ‘forward’).