1. The biologic association of two or more species.
2. The mutual cooperation or interdependence of two people, such as mother and infant, or husband and wife; sometimes used to denote excessive or pathologic interdependence of two people.
The information shown above for symbiosis is provided by Stedman's.
* Stedman's, part of Lippincott Williams & Wilkins, provide a comprehensive line of health-science publications for healthcare professionals and medical students.