[ myoo-choo-uh-liz-uh m ]
/ ˈmyu tʃu əˌlɪz əm /


a relationship between two species of organisms in which both benefit from the association.
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.
Sociology. the force or principle of mutual aid.

Origin of mutualism

First recorded in 1860–65; mutual + -ism


mu·tu·al·ist, nounmu·tu·al·is·tic, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for mutualist

  • Notably, the gilt catfish, which would undoubtedly die if deprived of its mutualist, the Gyropeltes.

British Dictionary definitions for mutualist

/ (ˈmjuːtʃʊəˌlɪzəm) /


another name for symbiosis

Derived forms of mutualism

mutualist, noun, adjectivemutualistic, adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for mutualist (1 of 2)

[ myōōchōō-ə-lĭst ]



Medicine definitions for mutualist (2 of 2)

[ myōōchōō-ə-lĭz′əm ]


A symbiotic relationship in which both species benefit.

Other words from mutualism

mu′tu•al•istic adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for mutualist

[ myōōchōō-ə-lĭz′əm ]

A relationship between two organisms in which each of the organisms benefits.♦ In obligate mutualism the interacting species are interdependent and cannot survive without each other. The fungi and algae that combine to form lichen are obligate mutualists.♦ In the more common facultative mutualism the interacting species derive benefit without being fully dependent. Many plants produce fruits that are eaten by birds, and the birds later excrete the seeds of these fruits far from the parent plant. While both species benefit, the birds have other food available to them, and the plants can disperse their seeds when the uneaten fruit drops. Compare amensalism commensalism parasitism.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.