(medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease
"The persistent headache was an early symptom of his developing migraine."
anything that accompanies X and is regarded as an indication of X's existence
"The persistent cough was a clear symptom of his developing lung infection."
A perceived change in some function, sensation or appearance of a person that indicates a disease or disorder, such as fever, headache or rash.
"The patient reported a persistent headache and high fever as the primary symptoms indicating she had contracted the flu."
In plain English: A symptom is any physical change that shows something might be wrong with your body.
"The patient went to see the doctor because she had a high fever and a bad headache, which were symptoms of the flu."
Usage: Use symptom to describe specific signs like pain or fatigue that indicate an underlying illness rather than the condition itself. Do not confuse it with sign, which refers to objective evidence observable by others without patient reporting.
The word "symptom" comes from the Ancient Greek súmpťoma, meaning an accident or a sign of disease. It is derived from a verb meaning "to befall," which combines a prefix for "together" with a root meaning "to fall."