Final answer:
A sign is an objective indication that a physician can evaluate, in contrast to subjective symptoms felt by the patient. Signs can be measured or confirmed clinically, such as through blood tests that detect antibodies.
Step-by-step explanation:
A sign is an objective indication that can be evaluated by a physician. Unlike symptoms, which are subjective and experienced by the patient, signs can be clinically confirmed or objectively measured. For instance, the presence of antibodies in a patient's serum is an observable condition that can be objectively measured through blood tests, making it a sign. To assist in evaluating symptoms, clinicians may use quantitative methods, such as the Wong-Baker Faces pain-rating scale for quantifying pain levels.