The word hematology comes from the Greek haima (means blood) and logos (means discourse); therefore, the study of hematology is the science, or study, of blood. Hematology encompasses the study of blood cells and coagulation. Included in its concerns are analyses of the concentration, structure, and function of cells in blood; their precursors in the bone marrow; chemical constituents of plasma or serum intimately linked with blood cell structure and function; and function of platelets and proteins involved in blood coagulation.