symptom

A symptom is a subjective experience reported by an individual that signals a deviation from normal function. It is distinguished from a sign, which is an objective finding observed by others, such as a clinician or a laboratory result. Because symptoms reflect personal perception, they can vary in quality, intensity, and meaning among people and are often nonspecific, occurring in many different diseases or conditions.

Symptoms are typically categorized as subjective experiences (felt by the patient) rather than objective signs (detected by examination). Common examples include pain, fatigue, nausea, dizziness, weakness, shortness of breath, and cognitive or mood changes. Clinicians collect symptom histories by asking about onset, location, quality, duration, severity, timing, and factors that worsen or relieve them.

Symptom information guides diagnosis and management. When combined with physical examination, laboratory tests, and imaging, symptoms help form a differential diagnosis. Because many symptoms overlap across conditions, clinicians use patterns and red flags—for example, sudden chest pain, severe headache with neurological symptoms, or abrupt weakness—to determine urgency and appropriate testing.

For optimal usefulness, symptoms should be accurately reported and documented. Patient-reported outcome measures, symptom checklists, and diaries are used in clinical care and research to track changes over time. Language, health literacy, and cultural factors can affect reporting, so clear, validated communication improves reliability.

The term symptom comes from the Greek symptoma, meaning “that which befalls” or “a manifestation.”