American Society of Hematology

Hematology Glossary


acute: refers to a disease that begins suddenly and/or progresses quickly

allogeneic: refers to blood, stem cells, bone marrow, or other tissue that is transferred from one person to another

anemia: a blood condition in which a person either does not have enough red blood cells or has red blood cells that do not function properly

antibody: a protein found in the blood that recognizes and binds to other substances. Helpful antibodies, such as those to viruses or bacteria, neutralize or destroy the target and prevent infection. Auto- or self-antibodies that work against a person's own red blood cells or platelets may cause destruction of these important blood components and cause disease.

anticoagulant: a drug that prevents blood clots from forming

antigen: a marker protein on cells of the body or foreign substances, such as a virus or bacteria

artery: a muscular vessel that carries oxygen- and nutrient-rich blood under high pressure from the heart to other parts of the body

arterial thromboembolism: a clot that forms within an artery and may obstruct the flow of blood

autologous: refers to blood or other tissue derived from a person's own body

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B lymphocyte: a type of white blood cell (also known as a B cell) that produces antibodies

basophil: a type of normal white blood cell that may increase with bone marrow damage, parasitic infections, or allergic reactions

benign: refers to a non-cancerous disease that does not spread throughout the body

bleeding disorder: the clinical problem that results when the blood does not clot properly

blood: the specialized fluid in your body that has many functions, including carrying oxygen and nutrients to other tissues, forming clots in response to injury, and carrying defensive cells and antibodies that fight infection

blood banking: the process of collecting, separating, and storing blood products

blood cancer: a condition (also known as a hematologic malignancy) that may affect the blood, bone marrow, or lymph nodes. Normal blood production and function is typically interrupted by the uncontrolled growth of an abnormal type of blood cell.

blood smear/film: the glass slide on which doctors look at blood cells under the microscope to determine if their appearance and number are normal 

blood transfusion: a procedure in which blood collected from a volunteer donor is transferred to another person

bone marrow: the soft, spongy tissue inside of bones where blood cells are produced

bone marrow transplantation: the transfer of healthy bone marrow cells into a person whose bone marrow is defective or has been damaged by chemotherapy or radiation

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cancer: an abnormal and uncontrolled growth of cells

capillaries: the body's smallest blood vessels, which connect arteries to veins

chimeric antigen receptor (CAR) T-cell therapy: a cancer immunotherapy whereby a patient’s primary immune cells (T-cells) are harvested, reengineered to target specific proteins on the surface of cancer cells, and reintroduced back into the patient’s immune system

chemotherapy: a medical treatment for the destruction of cancer cells

chronic: refers to a slowly progressing disease

circulatory system: the heart and network of blood vessels responsible for transporting blood throughout the body

clinical trial: a research study involving human volunteers to evaluate new ways to prevent, diagnose, manage, or treat medical problems or diseases

clot: a clump of platelets and blood proteins (also known as a thrombus) that form a plug at the site of an injured blood vessel to prevent excessive bleeding. A clot may also form inside a blood vessel and block that vessel, which is called a thrombosis or a blood clot.

coagulation: the process by which blood clots

complete blood count (CBC): a test that provides information about the types and numbers of cells in one's blood; health care professionals use the findings to diagnose conditions like anemia, infection, and other disorders

congenital: refers to a condition that is present at or before birth, even if there were no signs of the problem when the person was a child

cord blood stem cells: blood cells from the umbilical cord, collected from the placenta after the baby is born and separated from the mother, that have the unique property of self-renewal as well as the ability to develop into other types of cells; they may be used in stem cell transplants

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deep vein thrombosis: a type of blood clot that forms in a major vein of the leg or, less commonly, in the arms, pelvis, or other large veins in the bodyback to top


eosinophil:  a type of white blood cell   that mediates allergic reactions and defends the body from infection by parasites and bacteria

erythrocyte:  also called the red blood cell; the most abundant cell in the blood whose primary role is to carry the protein hemoglobin that transports oxygen from the lungs to the rest of the body 

erythropoietin:  a hormone produced primarily by the kidneys that controls the production of red blood cells


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factor:  a protein in the blood that is needed to form a blood clot

ferritin: a form of iron that is stored in the liver and released as needed to make new red blood cells

fibrin:  a threadlike protein that supports the formation of blood clots and provides the initial structure upon which new tissue can form at the site of an injury

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granulocyte: a type of white blood cell that includes neutrophils, eosinophils, and basophils back to top


hematocrit: the percentage of the whole blood volume that is made up of red blood cells; it is abbreviated Hct

hematologic malignancy: a disease (also known as a blood cancer) affecting the blood, bone marrow, or lymph nodes in which normal blood production and function is interrupted by the uncontrolled growth of an abnormal type of blood cell

hematologist: a physician who specializes in researching, diagnosing, and treating blood disorders

hematology: the scientific study of blood and blood-forming tissues

hematopoiesis: the process by which the body produces new blood cells

hematopoietic stem cell: a cell that can develop into any type of blood cell; often abbreviated HSC

hemoglobin: a protein in red blood cells that carries oxygen to other cells in your body; often abbreviated HGB, Hb, or Hg

hemoglobinopathy: a blood disease resulting from structural differences in hemoglobin produced by the body

hemophilia: a congenital or inherited bleeding disorder caused by a shortage of clotting factors in the blood

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idiopathic: refers to a disease or condition without a known cause

immune system: the network of cells, tissues, and organs that defend the body from infection and disease

intravascular hemolysis: a condition in which red blood cells break down in the blood stream

iron: a mineral that is important for maintaining many body functions and an integral part of hemoglobin, the molecule in your blood that carries oxygen to the tissues of the body

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leukemia: a type of cancer found in the blood and bone marrow that is caused by the production of abnormal white blood cells

leukocyte: a type of cell (also known as a white blood cell or WBC) in the blood that is primarily responsible for protecting the body from infection; there are five major types of white blood cells (basophils, eosinophils, lymphocytes, monocytes, and neutrophils), each with special properties and functions

lymph node: small organs throughout the body that play a role in the immune system by filtering out foreign particles, such as viruses and bacteria

lymphocyte: a type of white blood cell that plays a role in the immune system; there are two main populations of these cells: T lymphocytes, which help regulate the function of other immune cells and directly attack infected cells and tumors, and B lymphocytes, which make antibodies.

lymphocytic: refers to a disease involving the abnormal growth of white blood cells called lymphocytes

lymphoma: a type of blood cancer that occurs when abnormal lymphocytes (a type of white blood cell) multiply and collect in the lymph nodes and other tissues, impairing the function of the body's immune system

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malignant: refers to a cancerous tumor or disease that may spread or metastasize to other parts of the body

monocyte: a type of white blood cell that ingests bacteria and foreign particles

myelogenous: refers to a disease of the blood-forming cells in the bone marrow

myeloma: a cancer of plasma cells (white blood cells that produce disease- and infection-fighting antibodies)

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neutropenia: a low number of granulocytes (white blood cells that fight infection)

neutrophil: the most common type of white blood cell, which helps the body fight infection

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oncology: the scientific study of cancerback to top


peripheral blood: blood that is circulating through the body's blood vessels and heart

peripheral blood stem cells: rare cells in the peripheral blood that have the unique property of self-renewal as well as the ability to develop into other types of cells; these cells may be increased and used as the source of cells for a stem cell transplant

plasma: the liquid component of blood that transports blood cells throughout the body along with nutrients, waste products, antibodies, proteins, and chemical messengers such as hormones

plasma cell: a type of white blood cell that produces disease- and infection-fighting antibodies

platelet: a small cell fragment (also known as a thrombocyte) involved in the blood's clotting process

platelet count: part of the complete blood count, a blood test used to evaluate bleeding and clotting disorders

pulmonary embolism: a dangerous condition that occurs when a clot in a vein detaches from the blood vessel in which it formed and travels through the heart to the lungs where it becomes wedged, preventing adequate blood flow

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radiation therapy: a treatment used to destroy cancer cells with high-energy rays, such as x-rays or gamma rays

red blood cell: the most common blood cell; it carries the protein hemoglobin, which transports oxygen from the lungs to the rest of the body; red blood cells are also known as erythrocytes or RBC


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sickle cell anemia: a congenital inherited blood disorder characterized by a different type of hemoglobin that causes red blood cells to become rigid and sickle-shaped

stem cell: a cell that has the unique property of self-renewal as well as the ability to develop into other types of specialized cells, such as blood cells

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T lymphocyte: a type of white blood cell (also known as a T cell)that helps protect the body against infection and cancer; some T cells can also release substances to attract other white blood cells and can regulate the activity of other immune cells

targeted therapy: a type of treatment that destroys cancer cells without harming normal cells

thalassemia: an inherited congenital blood disorder that results in the decreased production of hemoglobin and red blood cells

thrombectomy: the surgical removal of a blood clot

thrombocyte: a small cell fragment (also known as a platelet) involved in the blood's clotting process

thrombosis: excess clotting, which may block veins or arteries

thrombus: a clump of platelets and blood proteins (also known as a clot) that form a plug at the site of an injured blood vessel to prevent excessive bleeding

transferrin: a protein that attaches to iron in the blood stream and delivers it to the liver

tumor: an abnormal mass of cells, which can be cancerous or benign

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vein: a vessel that carries blood low in oxygen away from the body's organs and back to the heart

venous thromboembolism: a clot that forms within a vein and may obstruct the flow of blood

von Willebrand disease: a bleeding disorder caused by decreased or abnormal von Willebrand factor, a blood protein that helps the blood to clot; it may be inherited or acquired

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white blood cell: a type of blood cell (also known as a leukocyte) that is primarily responsible for protecting the body from infection; there are five major types of white blood cells (basophils, eosinophils, lymphocytes, monocytes, and neutrophils), each with special properties and functions

white blood cell count (WBC): a bloodtest that measures the number of white blood cells to help detect problems in the body's immune system



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