Leukemia (British (British English)/Canadian English:leukaemia) (Greek leukos ?????? (wikt:??????), "white"; aima ???? (wikt:????), "blood") is a cancer of the blood or bone marrow and is characterized by an abnormal proliferation (production by multiplication) of blood cells (Cell (biology)), usually white blood cells (leukocytes). Leukemia is a broad term covering a spectrum of diseases. In turn, it is part of the even broader group of diseases called hematological neoplasms (Hematological malignancy).