sym·bi·o·sis (sĭm′bē-ōsĭs, -bī-)
n. pl. sym·bi·o·ses (-sēz)
1. Biology A close, prolonged association between two or more different organisms of different species that may, but does not necessarily, benefit each member.
2. A relationship of mutual benefit or dependence.
[Greek sumbiōsis, companionship, from sumbioun, to live together, from sumbios, living together : sun-, syn- + bios, life; see gwei- in the Appendix of Indo-European roots.]
sym′bi·otic (-ŏtĭk), sym′bi·oti·cal (-ĭ-kəl) adj.
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