A symptom (from Greekσύμπτωμα, "accident, misfortune, that which befalls", from συμπίπτω, "I befall", from συν- "together, with" + πίπτω, "I fall") is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality. A symptom is subjective, observed by the patient, and cannot be measured directly.
The term is sometimes also applied to physiological states outside the context of disease, as for example when referring to "symptoms of pregnancy".
Constitutional or general symptoms are those that are related to the systemic effects of a disease (e.g., fever, malaise, anorexia, and weight loss). They affect the entire body rather than a specific organ or location.
The terms "chief complaint", "presenting symptom", "iatrotropic symptom", or "presenting complaint" are used to describe the initial concern which brings a patient to a doctor. The symptom that ultimately leads to a diagnosis is called a "cardinal symptom".
Non-specific symptoms are those self-reported symptoms that do not indicate a specific disease process or involve an isolated body system. For example, fatigue is a feature of many acute and chronic medical conditions, whether physical or mental, and may be either a primary or secondary symptom. Fatigue is also a normal, healthy condition when experienced after exertion or at the end of a day.
Positive symptoms are symptoms that most individuals do not normally experience but are present in the disorder. It reflects an excess or distortion of normal functions (i.e., experiences and behaviours that have been added to a person’s normal way of functioning. Examples are hallucinations, delusions, and bizarre behavior.
Negative symptoms are functions that are normally found in healthy persons, but that are diminished or not present in affected persons. Thus, it is something that has disappeared from a person’s normal way of functioning. Examples are social withdrawal, apathy, inability to experience pleasure and defects in attention control.
Some symptoms 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 a significantly smaller number of possible causes than nausea does.
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.
Symptom versus sign
A symptom can more simply be defined as any feature which is noticed by the patient. A sign is noticed by other people. It is not necessarily the nature of the sign or symptom which defines it, but who observes it.
A feature might be a sign or a symptom, or both, depending on the observer(s). For example, a skin rash may be noticed by either a healthcare professional as a sign, or by the patient as a symptom. When it is noticed by both, then the feature is both a sign and a symptom.
Some features, such as pain, can only be symptoms, because they cannot be directly observed by other people. Other features can only be signs, such as a blood cell count measured in a medical laboratory.