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What Does "-osis" Mean?
Common "-osis" Words
Less Familiar "-osis" Words
The Bottom Line

They sound like words that people make up when imitating doctors: diverticulosis, osteochondromatosis, pneumoconiosis. These long, complicated words ending in "-osis" sound highly technical, even intimidating. But, their meanings are not as mysterious as they may seem. And, if your doctor uses one of these terms and doesn't explain its meaning, shame on him or her!

So, here's a short lesson on how to break these words down and translate them into something understandable. After all, there's little hope of understanding what your doctor is saying when the two of you are not speaking the same language.

What Does "-osis" Mean?

The ending "-osis" can have several meanings. Perhaps that's why it appears in so many medical words! These meanings can be grouped into two main categories:

An abnormality that occurs in multiples – Diverticulosis, for example, is a condition of the colon in which multiple diverticuli (outpouchings or sacs) have developed.
A condition or disease, often of a degenerative type – Common examples are spondylosis (spine degeneration) and tendinosis (tendon degeneration).

Not only does "-osis" have more than one meaning or usage, but other suffixes can have the same meaning. For example, "- opathy " means "disease" or "condition," too. Yet, medical terminology tends to use one or the other nearly exclusively, without a particular reason. So, you may hear an arthritis doctor talk about arthropathy (joint disease) but not arthrosis. On the other hand, we could refer to the hallucinations and delusions that are characteristic of psychosis (a disease of the "psyche," or mind) as psychopathy. But that's not how medical language has evolved.

Commons "-osis" Words

You might not realize it, but you probably already know many medical terms ending in "-osis" that are part of everyday language.

Cirrhosis – The term "cirrhoisis" comes from the Greek word, kirrhos, meaning yellow-brown, which describes the color of a liver that is scarred and not functioning properly.

Halitosis – This term means "bad breath," and comes from the Latin, halitus (breath).

Tuberculosis – This term refers to an infectious organism, Mycobacterium tuberculosis, a bacterium that tends to cause "tubercles" (small, rounded swellings) in the tissues it infects.

Less Familiar "-osis" Words

You may not have heard of the following medical terms unless you or someone you know has one of these conditions. But they follow the same pattern:

Endometriosis – In this condition, there is tissue from the uterus (womb) outside of its normal location; the term comes from "endometrium" (meaning inner lining of the uterus)

Hemochromatosis – This is a genetic disease in which there is excessive absorption of iron from the diet. Iron deposits cause damage in organs throughout the body; the term refers to the bronze discoloration of the skin and comes from hemo, which means "blood," and chroma, which means "color."

Osteochondromatosis – People with this relatively rare condition have "joint mice" or small pieces of joint tissue that have "ossified" (turned to bone). The term comes from osteo, which means "bone" and chondroma, which refers to cartilage that lines the joint.

Pneumoconiosis – This lung disease is caused by long-term inhalation of metallic or mineral dust; the name comes from pneumo (meaning lung) and konis (Greek root for dust).

Sarcoidosis – In this disease, inflamed lumps are found in one or more organs of the body, especially the lungs; because one of the first descriptions of the disease was of the rash it caused, it was called "sarcoid," meaning flesh-like (the way "humanoid" means human-like).

The words "diagnosis" and "prognosis" have similar origins in the Greek word gignoskein that means "to learn." Both also refer to the idea of "many possibilities." Dia means "apart" and pro means "before." "Diagnosis" means to distinguish among many possibilities and "prognosis" means to know in advance among many possible outcomes.

The Bottom Line

Think of all those "-osis" words as fancy ways of describing a condition where there's a lot of something that shouldn't be there or, simply, that a disease is present. Considering how technical many of these terms sound, their meaning is remarkably simple.

So, why not use simpler terms? I think the answer lies in the fact that all professionals — doctors, plumbers, astronauts — tend to have a language of their own. It gives the speaker credibility as a person "in the know" and helps others in the field instantly recognize the speaker's intent. The term "hemochromatosis," for example, means something more accurate or precise to another doctor than saying "iron overload."

Perhaps we should call the language doctors use medicalterminosis. Until a cure is found, learn what you can and ask your doctor about the rest.

Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

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