interrelationship

/ˌɪntərɪˈleɪʃənˌʃɪp/
noun
  1. A mutual connection or dependence between two or more things.
    • Understanding the interrelationship of different departments improves company efficiency.
    • The interrelationship between supply and demand determines prices.
    • Scientists study the interrelationship of all living things in an ecosystem.