noun: a reciprocal relation between interdependent entities (objects or individuals or groups)
CHAPTER XIII.
"Life implies this interdependence and harmonious interaction of parts, and the subordination of all to some universal plan." "Life and intelligence are powers, and rule; but Nature cannot create power, therefore life and intelligence are from a higher source."—J. W. Reynolds, M.A.
[Harmonies of Tones and Colours, Diagram X - Minor Keynotes Developing by Sevens, page 35a]