Core hematology vocabulary in plain English: blood cells, clotting and common blood disorders — defined for nursing and pre-med students.
Last updated: September 22, 2026
Hematology is the medical specialty devoted to the blood and blood-forming organs. Its vocabulary spans the cells that make up blood, the process of clotting, and the disorders that affect red cells, white cells and platelets. Mastering these terms is essential groundwork for nursing programs, pre-med coursework and any clinical role involving blood disorders.
| Term | Definition |
|---|---|
| Erythrocyte | A red blood cell that carries oxygen from the lungs to body tissues. |
| Leukocyte | A white blood cell that defends the body against infection. |
| Platelet | A small blood cell fragment that helps stop bleeding by forming clots. |
| Plasma | The pale yellow, liquid component of blood that carries cells, proteins and nutrients. |
| Hemoglobin | The iron-containing protein within red blood cells that binds and transports oxygen. |
| Hematocrit | The proportion of blood volume occupied by red blood cells. |
| Bone marrow | The soft tissue inside bones where blood cells are produced. |
| Spleen | The organ that filters blood, recycles old red blood cells and supports immune function. |
| Anemia | A condition characterized by a reduced capacity of the blood to carry oxygen, often due to a lack of red blood cells or hemoglobin. |
| Leukemia | A cancer of blood-forming tissue characterized by the abnormal proliferation of white blood cells. |
| Lymphoma | A cancer that originates in the lymphatic system. |
| Thrombocytopenia | An abnormally low number of platelets in the blood. |
| Leukocytosis | An abnormally high number of white blood cells in the blood. |
| Neutropenia | An abnormally low number of neutrophils, a type of white blood cell that fights bacterial infection. |
| Polycythemia | An abnormally high number of red blood cells in the blood. |
| Hemophilia | An inherited disorder in which the blood does not clot properly due to a deficiency of clotting factors. |
| Sickle cell disease | An inherited disorder in which red blood cells become rigid and crescent-shaped, impairing blood flow. |
| Thrombosis | The formation of a blood clot within a blood vessel. |
| Embolism | The blockage of a blood vessel by a clot or other material that has traveled from elsewhere in the body. |
| Hemolysis | The destruction or breakdown of red blood cells. |
| Coagulation | The process by which blood forms clots. |
| Hematoma | A localized collection of blood outside blood vessels, often caused by injury. |
| Purpura | Purple-colored spots on the skin caused by bleeding underneath it. |
| Phlebotomy | The practice of drawing blood from a vein for testing, donation or treatment. |
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Start learning free →Hematology vocabulary lets clinicians, students and patients describe blood cells, clotting and blood disorders precisely — from anemia to thrombosis — which is essential for accurate documentation and communication in blood-related care.
Yes. This vocabulary is core to US health programs — nursing school and NCLEX prep, pre-med, and medical assistant training. MediLearn lets you drill these terms with quizzes and flashcards using spaced repetition.
The pale yellow, liquid component of blood that carries cells, proteins and nutrients.
An abnormally high number of white blood cells in the blood.
The destruction or breakdown of red blood cells.