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[L. functio, stem function-, performance]

1. The action performed by a structure. In a living organism this may pertain to a cell or a part of a cell, tissue, organ, or system of organs.
2. The act of carrying on or performing a special activity. Normal function is the normal action of an organ. Abnormal activity or the failure of an organ to perform its activity is the basis of disease or disease processes. Structural changes in an organ are pathological and are common causes of malfunction, although an organ may function abnormally without observable structural changes. In humans, function can pertain to the manner in which the individual can perform successfully the tasks and roles required for everyday living.

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