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 sumbisis, companionship, from sumbioun, to live together, from sumbios, living together : sun-, syn- + bios, life; see gwei- in Indo-European roots.]
symbi·otic, symbi·oti·cal | adj.
symbi·oti·cal·ly | adv.
sym·bi·o·ses | pl.