| Term | Definition |
| Agranular leukocytes | White blood cells that lack visible granules in their cytoplasm; include lymphocytes and monocytes. |
| Basophils | A type of granulocyte involved in inflammatory and allergic responses; release histamine and heparin. |
| Eosinophils | Granulocytes that help fight parasitic infections and are involved in allergic reactions. |
| Erythrocyte | A red blood cell responsible for transporting oxygen and carbon dioxide in the blood. |
| Granular leukocytes | White blood cells with visible cytoplasmic granules (neutrophils, eosinophils, basophils). |
| Hematopoiesis | The process of forming all types of blood cells in the bone marrow. |
| Hemoglobin | An iron-containing protein in red blood cells that binds and transports oxygen. |
| Leukocytes | White blood cells involved in immune defense. |
| Lymphoid | Refers to a lineage of blood cells that develop into lymphocytes and related cells. |
| Monocytes | Large agranular leukocytes that differentiate into macrophages and dendritic cells in tissues. |
| Myeloid | Refers to a lineage of blood cells that includes erythrocytes, platelets, and most leukocytes (except lymphocytes). |
| Neutrophils | The most abundant granulocytes; first responders to infection, especially bacterial. |
| Plasma | The liquid component of blood that carries cells, nutrients, hormones, and waste products. |
| Platelets | Cell fragments involved in blood clotting; also called thrombocytes. |
| Pluripotent hematopoietic (stem cells) | Stem cells in bone marrow that can differentiate into all types of blood cells. |
| Red blood cells (RBCs) | Cells that carry oxygen via hemoglobin; another term for erythrocytes. |
| Thrombocytes | Another name for platelets; involved in clot formation. |
| White blood cells (WBCs) | Cells of the immune system that defend against infection; also called leukocytes. |