Diabetes usually refers to diabetes mellitus.
Diabetes mellitus is a medical disorder in which blood sugar is above normal level. Passing excessive urine and frequent thirst are its common symptoms.

Diabetes is a Greek word meaning "a compass, siphon" as the name for a distressing symptom of the disease, that is the discharge of excessive amounts of urine. Mellitus comes from the Greek word "sweet" because the urine of the diabetic patients attracted flies and bees due to the high glucose content.