So are there any words that differentiate foreign bodies in the human body that between neutral, beneficial, and disadvantageous foreign bodies.

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    Can you explain why neutral, beneficial, and disadvantageous foreign bodies isn't good enough? Feb 22 '18 at 21:51
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    Are you thinking more about differentiating between (for example) two different bacteria, one that aids my digestion and the other that makes the scrape on my arm all red, puffy, and painful; or are thinking more about differentiating between the bullet in my shoulder and the supportive plate the surgeon used to patch together the pieces of my shattered tibia? (Speaking hypothetically of course, I am bullet-free and my tibia in one piece).
    – cobaltduck
    Feb 22 '18 at 21:51
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    @marcellothearcane In technical fields like medicine, there may very well be specific one-word terms for abstruse concepts. The OP is not looking for suggestions for new words or something that might communicate the meaning to non-specialists, but for how the medical community currently refers to these concepts.
    – Mitch
    Feb 22 '18 at 23:42
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    Any artificial device inserted into the human body by an MD or a DDS to replace a diseased or impaired part of an organ is called a prosthesis. It can be a prosthetic valve, a hip prosthesis or a penile prosthesis.
    – Centaurus
    Feb 23 '18 at 0:20
  • Any other nonliving thing, is a foreign body.
    – Centaurus
    Feb 23 '18 at 0:22

In addition to Edwin's post (where all the terms can be made into nouns quite easily if that's what is needed), I would also like to add:

  • "parasite" (a foreign body which feeds off of and/or relies on its host for survival, to the host's body's detriment: leeches, ticks, intestinal worms, a foetus...)

  • "Symbiont" (like a parasite, only it helps its host: our gut flora that help us digest foods, for example, or a clown fish living in a sea anemone.)

(I can't recall if there is a third option where the effect to the host is neutral. Grade 9/10 science was a long time ago. Though note: these all describe relationships where an organism depends on the host, be that host a human body or otherwise).

  • a "parasite" is usually referred to as an organism; be it a microorganism ( bacteria, fungi or protozooa) , a large multicellular organism (helminths) or an ectoparasite (the itch mite). Better use the term "microorganism than "foreign body". Foreign bodies are not living organisms.
    – Centaurus
    Feb 23 '18 at 0:10
  • Thank you. I am aware that parasites and symbionts refer to organisms. However, there is some general confusion as to what exactly the OP is looking for, including in what sense they mean "foreign body" (are they using it correctly, or not? We don't have examples to know for sure yet). So just to be on the cautious side, I figured it would be worth it to add, in case it helps them find what they're looking for.
    – Iolite_Jay
    Feb 23 '18 at 0:17

pathological has the sense 'relating to disease' and this sense is the default one in 'pathological organisms'.

pathological: (2) Involving or caused by a physical or mental disease [ODO]

pathogenic also means 'causing disease'


... infectious disease that can be spread by any pathological organism transmitted by and to humans ... [CourseHero]


benign means 'not harmful' in this context.

benign: ...

1a Having little or no detrimental effect; harmless

b Of no danger to health; not malignant or disease-causing [AHD]


beneficial is commonly used for foreign organisms that actually benefit the host.

Beneficial Bacteria:

Bacteria are the most abundant form of life on the planet. They are found in most every environment, from Antarctic ice, to boiling hydrothermal vents, to inside your stomach. Most of these do not hurt us. Actually, many of these organisms are very important to our survival. [ASU: Ask a biologist]

  • The question - especially the title - suggests the OP is looking for nouns (pathogen, etc).
    – Lawrence
    Feb 22 '18 at 22:47
  • We await clarification, in line with – marcellothearcane's 'Can you explain why "neutral, beneficial, and disadvantageous foreign bodies" isn't good enough?' But this answer uses an interpretation of the original that cannot be arrogated to be incorrect, and seems to be useful. It gives idiomatic answers. Ones often used. Feb 22 '18 at 22:56

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