Definition of symbiont in US English:



  • Either of two organisms that live in symbiosis with one another.

    • ‘Also unknown is whether chemicals that function as signals, rather than as nutrients, pass from the symbionts to the host organism.’
    • ‘Some organisms have enlisted symbionts to provide traits or functions found in other kingdoms.’
    • ‘An association between mitochondria and intracellular symbionts has already been documented for other symbiotic bacteria that manipulate host reproduction.’
    • ‘The aphids can also host one of several bacterial symbionts known as secondary symbionts.’
    • ‘She convinced the cytologists that mitochondria are symbionts in both plant and animal cells, as are chloroplasts in plant cells.’


Late 19th century: formed irregularly from Greek sumbiōn ‘living together’, present participle of sumbioun (see symbiosis).