Which statement correctly defines a symptom?

A symptom is defined as subjective evidence of a disease. This means it is a manifestation of a disease that cannot be directly observed or measured by a healthcare provider, but is reported by the patient experiencing it. For example, feelings of pain, fatigue, or nausea are all symptoms that patients express and are based on their personal experiences.

This definition is critical in healthcare as it helps distinguish between what patients feel and what can be observed clinically. Symptoms prompt further investigation and can guide clinicians in making a diagnosis. The other options relate to objective findings or tests that provide measurable data regarding health, but they do not capture the patient's perspective, which is essential for understanding the full picture of an individual's health status.