What is the medical term for white blood cells?

The medical term for white blood cells is leukocytes. The word comes from Greek roots meaning “white” and “cell,” reflecting the pale appearance of the layer where these cells collect when blood is separated in a laboratory.

Leukocytes are immune-system cells that help defend the body against infections, abnormal cells, and foreign substances. They are produced mainly in the bone marrow and circulate through the blood, lymphatic system, and tissues. Major groups include granulocytes, lymphocytes, and monocytes, each with distinct roles in immune defense.

Lymphocytes are therefore not a synonym for every white blood cell; they are one type of leukocyte. Erythrocytes are red blood cells, while thrombocytes are platelets. A complete blood count measures white-cell levels because unusually high or low counts can signal infection, inflammation, immune problems, or other disease. In routine medical writing, “white blood cells,” “white cells,” and “leukocytes” refer to the same broad cell group.