Reciprocity is a noun that means mutuality, representing the characteristic of what is reciprocal.
Reciprocity is an essential feature in friendship and love relationships. Each person should be able to reciprocate feelings of love and friendship toward others, and share what they have, as well as be able to demonstrate and reciprocate that friendship through actions, not just words. For example, we can name the friends described in the question above, who always share what they have with each other. Such a friendship is not endowed with reciprocity.
