commensal

1. not comparablebiologyOf a form of symbiosis in which one organism derives a benefit while the other is unaffected.

   The fish (AMPHIPRION PERCULA) "intel-intel" of the blacks, is said to be commensal (literally, dining at the same table with its host), as distinguished from the parasite, which lives on its host.

   1911, E. J. Banfield, chapter XIII, in My Tropic Isle

   1 more example

   With this there is also associated the grazing or herding over wider or more restricted areas, belonging either collectively or discretely to the community, of sheep, cattle, goats, or swine, and almost always the domestic fowl is commensal with man in this life.

   1914, H. G. Wells, “The Great State”, in An Englishman Looks at the World […] , Cassell & Co

2. not comparableEating at the same table.

plural commensals

1. biologyAn 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, →ISBN, page 260

2. One who eats at the same table.

   Colville ordered it, and was sorry when the last of his commensals, slightly bowing him a good-night, left him alone to it.

   1886, William Dean Howells, Indian Summer

   2 more examples

   Around this tragic central figure are grouped the commensals of the Vauquer pension, Rastignac, the young law-student, with shallow purse and aristocratic connections; […].

   1910, Frederick Lawton, Balzac

   More than once I sat down to lunch or dinner with brilliant commensals, one of whom was understood to have made away with a well-known personage in order to rid the state of a bad administrator, and another had, at a secret Vehmgericht in Turkey, condemned a friend of mine, now a friend of his, to be assassinated.

   1920, Emile Joseph Dillon, The Inside Story of The Peace Conference, Harper & Brothers