A symptom (from Greek σύμπτωμα, “accident, misfortune, that which befalls”, from συμπίπτω, “I befall”, from συν- “together, with” and πίπτω, “I fall”) is a departure from normal function or feeling which is noticed by a patient, reflecting the presence of an unusual state, or of a disease. A symptom is subjective, observed by the patient, and cannot be measured directly, whereas a sign is objectively observable by others. For example, paresthesia is a symptom (only the person experiencing it can directly observe their own tingling feeling), whereas erythema is a sign (anyone can confirm that the skin is redder than usual). Symptoms and signs are often nonspecific, but often combinations of them are at least suggestive of certain diagnoses, helping to narrow down what may be wrong. In other cases they are specific even to the point of being pathognomonic.
The term is sometimes also applied to physiological states outside the context of disease, as for example when referring to “symptoms of pregnancy”. Many people use the term sign and symptom interchangeably.
The science that studies the symptoms of diseases.
All the symptoms of a particular disease.
the set of symptoms characteristic of a medical condition or exhibited by a patient.