commensal

Etymology

From Middle English commensal, from Old French commensal, from Medieval Latin commensālis, from com- + mensa (“table”) + -ālis.

adj

1. (ecology) Of a form of symbiosis in which one organism derives a benefit while the other is unaffected.
2. Eating at the same table.

noun

1. (ecology) An organism partaking in a commensal relationship.
   The tree did indeed grow right out of the algae, as I had seen from the lifeboat. There was not the least trace of soil. Either there was soil deeper down, or this species of tree was a remarkable instance of a commensal or a parasite. 2001, Yann Martel, Life of Pi, Canongate, published 2003, page 260
2. One who eats at the same table.