symbiosis

Bah, wikipedia. The work of ideologues and heathens!

Actually that is interesting. Thank you, signor.

As Wikipedia well explains, symbiosis is now generally used in a wider sense... Symbiosis sensu stricto can be more narrowly called mutualism.

Isn't reciprocity the essence of symbiosis? Parasitic and symbiotic relationships are mutually exclusive.

Parasitic relationships are a kind of symbiosis, too - a kind with no reciprocity.

Not necessarily, no. In fact if you have two organisms each consuming the other, it wouldn't be symbiotic because one or both would die as a result. But you might be thinking, for example, of those little fish that eat the parasites off sharks. The little fish get fed, and the shark gets rid of its parasites.

Isn't it a feeding off of one another?

No, seriously, jmp! The word symbiosis, for many reasons, is now used again in its literal meaning of "living together".
I would not insist, but this is a field I know quite well - and I love. :-)

No, I think it's the opposite. Symbiosis is the case where the whole is greater than the sum of its parts.

Well spotted. Symbiotic has a more correct definition, while this one is more naïve and old-fashioned.

Why is the head definition for this word the opposite of the head definition for its adjective, symbiotic?