<p><strong>Noun:</strong></p><ul><li>A relationship between two species of organisms in which both benefit from the association.</li><li>The doctrine that the interdependence of social elements is the primary determinant of individual and social relations, especially the theory that common ownership of property, or collective effort and control governed by sentiments of brotherhood and mutual aid, will be beneficial to both the individual and society.</li><li>Sociology: The force or principle of mutual aid.</li></ul>