Symptom

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The term symptom (from the Greek σύμπτωμα meaning 'chance', 'mishap' or 'casualty', itself derived from συμπιπτω meaning 'to fall upon' or 'to happen to') has two similar meanings in the context of physical and mental health:

Strictly, a symptom is a sensation or change in health function experienced by a patient. Thus, symptoms may be loosely classified as strong, mild or weak. In this, medically correct, sense of the word, it is a subjective report, as opposed to a sign, which is objective evidence of the presence of a disease or disorder. Examples of symptoms are fatigue/tiredness, pain, or nausea. In contrast, elevated blood pressure, or abnormal appearance of the retina, would be a medical sign indicating the nature of the disease.

A symptom may loosely be said to be a physical condition which indicates a particular illness or disorder (e.g. Longman, 1995). An example of a symptom in this sense of the word would be a rash. However, correctly speaking, this is known as a sign, as would any indication detectable by a person other than the sufferer without verbal information from the patient.

Some symptoms, such as nausea, occur in a wide range of disease processes, whereas other symptoms are fairly specific for a narrow range of illnesses. For example, a sudden loss of sight in one eye has only a very limited number of possible causes.

Some symptoms can be misleading to the patient or the medical practitioner caring for them. For example, inflammation of the gallbladder often gives rise to pain in the right shoulder, which may understandably lead the patient to attribute the pain to a non-abdominal cause such as muscle strain, rather than the real cause.

The terms "chief complaint", "presenting symptom", or "presenting complaint" is used to describe the initial concern which brings a patient to a doctor. The symptom that leads to a diagnosis is called a cardinal symptom.

A symptom can more simply be defined as any feature which is noticed by the patient. A sign is noticed by the doctor or others. It is not necessarily the nature of the sign or symptom which defines it, but who observes it. Clearly then, the same feature may be noticed by both doctor and patient, and so is at once both a sign and a symptom. The distinction is as simple as this, and therefore it may be nonsensical to argue whether a particular feature is a sign or a symptom. It may be one, the other, or both, depending on the observer(s). Some features, such as pain, can only be symptoms. A doctor cannot feel a patient's pain (unless he is the patient!). Others can only be signs, such as a blood cell count measured by a doctor or a laboratory.

In engineering, "symptom" may be used to refer to an undesired effect occurring in a system. To eliminate the effect, a root cause analysis is performed which traces the symptom to its cause and again through the cause's cause and so on until the subsystem is identified that can be changed to eliminate the symptom.