1. An inherited form of anemia occurring chiefly among people of Mediterranean descent, caused by faulty synthesis of part of the hemoglobin molecule.
2. A hereditary form of anemia, particularly prevalent around the Mediterranean, that is caused by a dysfunction in the synthesis of the red blood pigment hemoglobin.

Not just one disease but rather a complex series of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen.