Glossary try the best to avoid the use of medical terms that could make it more difficult to understand the information on this website. Still, there are a number of terms that can't be avoided and that are useful to know because they are so often used by the doctors, nurses, and other medical professionals with whom you might speak. The list below includes the terms used on for which we have provided definitions.

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Term Definition

Also known as: Microbe

Life form that is not visible to the naked eye such as bacteria, fungi, parasites, and viruses


a growth on the skin comprised of a cluster of skin cells that produce the skin pigment melanin (melanocytes); a mole is often raised and dark in color.

Monoclonal antibody

Antibody produced by or derived from a single type (clone) of plasma cell

Monoclonal cells

Group of cells derived from a single type (clone) of cell; the cells formed are identical.

Monoclonal gammopathy

Leukocyte (white blood cell) that functions in the ingestion of bacteria and other foreign particles. Monocytes make up 5-10% of the total white blood cell count.


Pertaining to system of bones, muscles, joints, and associated tissues (e.g., ligaments and tendons) of the body involved in the maintenance of body form and movement


Change in the genetic structure (DNA); it may occur spontaneously or be induced (e.g., by radiation, drugs, or certain mutagenic chemicals).


A diverse group of rod-shaped bacteria that include Mycobacterium tuberculosis (which causes tuberculosis) and Mycobacterium leprae (which causes leprosy) and more than 100 different species found in the environment; the environmental mycobacteria may be referred to as nontuberculous mycobacteria (NTM), mycobacteria other than tuberculosis (MOTT), and/or atypical mycobacteria.


Also known as: Myelin sheath

The fatty covering that insulates nerve fibers

Myelin sheath

Also known as: Myelin

The fatty covering that insulates nerve fibers