Definition of commensal in English:



  • Relating to or exhibiting commensalism.

    • ‘The majority of reports came from Europe but resistance in commensal rodents was also documented in the United States, Canada, Japan, and Australia.’
    • ‘Based on this finding it was suggested that this bacterial strain has at least a commensal relationship with the host.’
    • ‘The outermost layer - the epidermis, is colonised by a raft of commensal bacteria, that is, bacteria that generally don't cause harm to the host.’
    • ‘We saw several fist-sized sea squirts which were bright pink in colour, and only when studying the photographs afterwards noticed that each was attended by a number of well-camouflaged commensal prawns, also pink.’
    • ‘Aids, for example, infects some primates without causing illness or death, and has probably lived in them in a commensal relationship for generations.’


  • A commensal organism, such as many bacteria.

    • ‘This species is also closely associated with colonies of various seabirds and marine mammals; it feeds among birds and seals and has been considered a commensal of those colonial animals.’
    • ‘However, their isolates were from sites such as the nose and hands of the foodhandlers, where these organisms remain as mere commensals.’
    • ‘In an editorial review on the relationship of bacteria to lung host defenses, it was suggested that it should be possible to separate the presence of bacteria as commensals in the airway from those causing an infection.’
    • ‘It may be that their main metabolic interaction is with bacterial commensals, rather than directly with the insect host.’
    • ‘At least one report suggests that the number of bacterial strains that are symbiotic or commensal is limited.’


Late 19th century: from medieval Latin commensalis, from com- sharing + mensa a table.