\Sym`bi*o"sis\, n. [NL., fr. Gr. ? a living together,
? to live together; ? with + ? to live.] (Biol.)
The living together in more or less imitative association or
even close union of two dissimilar organisms. In a broad
sense the term includes parasitism, or
{antagonistic, or antipathetic, symbiosis}, in which the
   association is disadvantageous or destructive to one of
   the organisms, but ordinarily it is used of cases where
   the association is advantageous, or often necessary, to
   one or both, and not harmful to either. When there is
   bodily union (in extreme cases so close that the two form
   practically a single body, as in the union of alg[ae] and
   fungi to form lichens, and in the inclusion of alg[ae] in
   radiolarians) it is called
{conjunctive symbiosis}; if there is no actual union of the
   organisms (as in the association of ants with
   myrmecophytes),
{disjunctive symbiosis}.