Signs are different from symptoms, the subjective experiences, such as fatigue, that patients might report to their examining physician.

For convenience, signs are commonly distinguished from symptoms as follows: Both are something abnormal, relevant to a potential medical condition, but a symptom is experienced and reported by the patient, while a sign is discovered by the physician during examination of the patient.

According to Lester S. King, author of Medical Thinking, it is an “essential feature” of a sign that there is both a sign and a “thing signified”. And, because “the essence of a sign is to convey information”, it can only be a sign if it has meaning. Therefore, “a sign ceases to be a sign when you cannot read it”.

A slightly different definition views signs as any indication of a medical condition that can be objectively observed (i.e., by someone other than the patient), whereas a symptom is merely any manifestation of a condition that is apparent to the patient (i.e., something consciously affecting the patient). From this definition, it can be said that an asymptomatic patient is uninhibited by disease. With this set of definitions, there is some overlap – certain things may qualify as both a sign and a symptom (e.g., a bloody nose).