Sayid’s liver is not able to break down harmful substances in his body, which is an important function of the liver. Sayid’s condition is best classified as

Sayid’s liver is not functioning normally: it cannot break down harmful substances, a job the liver normally performs. An abnormality in how an organ functions is best classified as a disorder. A symptom is something a person experiences, while a sign is an observable finding; neither describes the liver’s impaired function here.

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