Cytopenia is a reduction in the number of blood cells. It takes a number of forms:
Low red blood cell count: resulting in anemia.
Low white blood cell count: leukopenia or neutropenia (because neutrophils make up at least half of all white cells, they are almost always low in leukopenia).
Low platelet count: thrombocytopenia.
Low granulocyte count: granulocytopenia
Low red blood cell, white blood cell, and platelet counts: pancytopenia.