In medicine, a sign is a feature of disease as detected by the doctor during physical examination of a patient. It is therefore "objective", as opposed to the patient's experience (symptom), which is (relatively) subjective.

Examples of signs are elevated blood pressure, or abnormal appearance of the retina, or clubbing of the fingernails. These would generally be meaningless to the patient, but can prompt the doctor to look for certain categories of diseases to explain the patient's symptoms.

A number of signs are named after the doctors who first observed them. See list of eponymous medical signs for a larger list.

Some specific signs:

• Ascites (fluid in the abdomen)
• Caput medusae (dilated umbilical veins)
• Clubbing (deformed nails)
• Cough
• Dysphagia (difficulty eating)
• Dysuria (difficulty urinating)
• Fever
• Gynecomastia (excessive breast tissue in males)
• Hemoptysis (blood-stained sputum)
• Hepatosplenomegaly (enlarged liver and spleen)
• Icterus ("jaundice")
• Lymphadenopathy (swollen lymph nodes)
• Palmar erythema (reddening of hands)
• Sleep hyperhidrosis ("night sweats")
• Splenomegaly (enlarged spleen)
• Vomiting