Final answer:
Pain is often referred to as the fifth vital sign. It is a subjective symptom of disease and cannot be clinically confirmed or objectively measured.
Step-by-step explanation:
Pain is often referred to as the fifth vital sign. Unlike signs, symptoms of disease are subjective, meaning they are felt or experienced by the patient but cannot be clinically confirmed or objectively measured. Pain is a symptom that can vary in intensity and can indicate the presence of an underlying condition or injury.