Sign has the following meanings in the field of medicine:

1. A clear evidence of disease that can be measured or
observed. Examples of common signs include fever, rash,
sweating, vomiting, tremor (shaking), and swelling. Unlike
signs, symptoms are an indication of a disease or a
change in condition that are not observed by others, such
as feeling pain. Signs can indicate the presence of
symptoms, such as when scratching (a sign) indicates
the presence of an itching sensation (a symptom). 
These blisters are a classic
sign of the chicken pox illness.
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Syndromes are a group of signs and symptoms that occur together and have a common
cause, representing a certain disease or inherited abnormality.

Signs can be observed by healthcare providers during physical examination or
behavioral observations but all healthcare providers should be aware that certain signs
(e.g., shaking, stuttering) can be exaggerated by patients in certain situations.
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2. One of many movements of the body or arms
and legs that are used to express something and
represent a language. An example would be when
someone uses to hands to grab their throat, which
is a sign indicating that the person is choking.

3. In psychology, a sign is something that
represents a specific idea to the person who
perceives it.

4. A symbol or abbreviation. Sign comes from the
Latin word “signum” meaning “mark.”