Interaction /(?)/

In·ter·ac·tion

Interaction

n.
  1. Intermediate action.
  2. Mutual or reciprocal action or influence; as, the interaction of the heart and lungs on each other.
  3. The effect, such as exertion of a force, that one object exerts on another, especially the capture or emission of a particle. (Physics)
  4. Communication between people, or the actions of people that affect others.