CA-125 test  - blood test to detect an elevated level of a protein antigen called CA-125, which may indicate ovarian cancer, among other disorders.

Calcium channel blocker (Also called calcium blocker.) - a medication used to treat heart disease.

Calculi - stones or solid lumps such as gallstones.

Calluses - thick, hardened areas of the skin, usually on the foot, caused by friction or pressure.

Campylobacter pylori - original name for the bacterium that causes ulcers; new name is Helicobacter pylori.

Cancellous tissue - the sponge-like tissue inside bones.

Cancer - abnormal cells that divide without control, which can invade nearby tissues or spread through the bloodstream and lymphatic system to other parts of the body.

Candidiasis - mild infection caused by the Candida fungus, which lives naturally in the gastrointestinal tract. Infection occurs when a change in the body, such as surgery, causes the fungus to overgrow suddenly.

Capillaries - tiny blood vessels between arteries and veins that distribute oxygen-rich blood to the body.

Capsule - the layer of cells around an organ, such as the capsule of the prostate.

Captioning - text display of spoken words presented on a television or a movie screen that allows a deaf or hard-of-hearing viewer to follow the dialogue and the action of a program simultaneously.

Carcinogen - a substance that is known to cause cancer.

Cardiac - pertaining to the heart.

Cardiac arrest - the stopping of heartbeat.

Cardiac output - total amount of blood being pumped by the heart over a particular period of time.

Cardiology - the clinical study and practice of treating the heart.

Cardioversion - the procedure of applying electrical shock to the chest to change an abnormal heartbeat into a normal one.

Caroli's disease - An inherited condition in which bile ducts in the liver are enlarged and may cause irritation, infection, or gallstones.

Carotid arteries - the major arteries in the neck that supply blood to the brain.

Cartilage - a smooth material that covers bone ends of a joint to cushion the bone and allow the joint to move easily without pain.

Cathartics - laxatives.

Catheter - a flexible tube used to drain fluid from or inject fluid into the body. The most common catheter is the Foley catheter, used to drain urine from the bladder.

Cecostomy - tube that goes through the skin into the beginning of the large intestine to remove gas or feces; it is a short-term way to protect part of the colon while it heals after surgery.

Cecum - beginning of the large intestine; it is connected to the lower part of the small intestine, called the ileum.

Cellular pathology (Also called cytopathology.) - the study of cellular alterations in disease.

Central auditory processing disorder - inability of individuals with normal hearing and intelligence to differentiate, recognize, or understand sounds.

Cerebellum - a large structure consisting of two halves (hemispheres) located in the lower part of the brain; responsible for the coordination of movement and balance.

Cerebral embolism - a blood clot from one part of the body that is carried by the bloodstream to the brain where it blocks an artery.

Cerebral hemorrhage - bleeding within the brain.

Cerebral thrombosis - formation of a blood clot in an artery that supplies blood to the brain.

Cerebrovascular - pertaining to blood vessels in the brain.

Cerebrovascular accident (Also called stroke.) - an impeded blood supply to the brain.

Cerebrovascular occlusion - an obstruction in the blood vessel in the brain.

Cerebrum - consists of two parts (lobes), left and right, which form the largest and most developed part of the brain; initiation and coordination of all voluntary movement take place within the cerebrum. The basal ganglia are located immediately below the cerebrum.

Cervical intraepithelial neoplasia (CIN) - term used to classify the degree of precancerous change in cells of the cervix in a condition called cervical dysplasia.

Cesarean delivery (Also called cesarean section or C-section.) - surgical procedure to deliver a baby through an incision in the lower abdomen and uterus.

Chemosensory disorders - disorders or diseases of smell and/or taste.

Chlorhydria - too much hydrochloric acid in the stomach.

Cholangiography - series of x-rays of the bile ducts.

Cholecystitis - inflammation of the gallbladder wall.

Cholecystokinin - hormone released in the small intestine; causes muscles in the gallbladder and the colon to tighten and relax.

Cholelithiasis - a condition in which gallstones are present in the gallbladder.

Chorea - rapid, jerky, dance-like movement of the body.

Chyme - thick liquid made of partially digested food and stomach juices; made in the stomach and moves into the small intestine for further digestion.

Cineangiography - a procedure that  involves taking moving pictures to show the passage of dye through blood vessels.

Circulatory system - pertaining to the heart and blood vessels, and the circulation of blood.

Claudication - pain or fatigue in arms and legs due to a poor supply of oxygen to the muscles.

Clinical trials - studies, involving patients, aimed at finding better ways to prevent, detect, diagnose, or treat cancer.

Clostridium difficile (Also called C. Difficile.) - bacteria naturally present in the large intestine that make a substance that can cause a serious infection, called pseudomembranous colitis, in people taking antibiotics.

Coccydynia - pain around the coccyx.

Cochlea - snail-shaped structure in the inner ear that contains the organ of hearing.

Cochlear implant - medical device that bypasses damaged structures in the inner ear and directly stimulates auditory nerves to allow some deaf individuals to learn to hear and interpret sounds and speech.

Colectomy - partial or complete removal of the large bowel or colon.

Colon - large intestine.

Colon polyps - small, fleshy, mushroom-shaped growths in the colon.

Colonic inertia - condition of the colon when muscles do not work properly, causing constipation.

Colonoscopic polypectomy - removal of tumor-like growths (polyps) using a device inserted through a colonoscope.

Colony-stimulating factors - substances that stimulate the production of blood cells.

Coloproctectomy - proctocolectomy.

Colorectal cancer - cancer that occurs in the colon (large intestine) or the rectum (the end of the large intestine).

Colorectal transit study - test to see how food moves through the colon.

Colostrum - thin, white, first milk produced by the breasts during late pregnancy and for a few days after childbirth. It provides a nursing infant with essential nutrients and infection-fighting antibodies.

Common bile duct - tube that carries bile from the liver to the small intestine.

Common bile duct obstruction - blockage of the common bile duct, often caused by gallstones.

Compact tissue - the harder, outer tissue of bones.

Comparative pathology - the study of disease in animals and how it compares in humans.

Complementary medicine - any form of therapy used in combination with other alternative treatments or standard/conventional medicine.

Composite resins (Also called white fillings.) - a tooth-colored plastic mixture filled with glass (silicon dioxide) that is used primarily for cosmetic improvements of the smile by changing the color of the teeth or reshaping disfigured teeth.

Computed tomography (CT or CAT scan) - a non-invasive procedure that takes cross-sectional images of the brain or other internal organs; to detect any abnormalities that may not show up on an ordinary x-ray.

Conductive hearing impairment - hearing loss caused by dysfunction of the outer or middle ear.

Cone biopsy (Also called conization.) - a biopsy in which a larger cone-shaped piece of tissue is removed from the cervix by using the loop electrosurgical excision procedure or the cold knife cone biopsy procedure.

Constrict - tighten; narrow.

Continence - ability to hold in a bowel movement or urine.

Continent ileostomy - operation to create a pouch from part of the small intestine. Stool that collects in the pouch is removed by inserting a small tube through an opening made in the abdomen.

Contractions, labor - rhythmic tightening of the muscular wall of the uterus to push the fetus down through the vagina during childbirth.

Contusion - a bruise caused by a blow to the muscle, tendon, or ligament; caused when blood pools around the point of injury and discolors the skin.

Cornea - the clear, dome-shaped surface that covers the front of the eye.

Corneal curvature - the shape of the front surface of the eye.

Coronary artery bypass graft (CAB or CABG) - a surgical procedure in which a healthy blood vessel is transplanted from another part of the body into the heart to replace or bypass a diseased vessel.

Coronary heart disease - a condition in which the coronary arteries narrow from an accumulation of plaque (atherosclerosis) and cause a decrease in blood flow.
Coronary occlusion - an obstruction of one of the coronary arteries that decreases flow to the heart muscle.

Coronary thrombosis - the formation of a clot in one of the arteries that carry blood to the heart muscle.

Cortex - the outer layer of the cerebrum, densely packed with nerve cells.

Corticosteroids - potent anti-inflammatory hormones that are made naturally in the body or synthetically for use as drugs. The most commonly prescribed drug of this type is prednisone.

Craniectomy - excision of a part of the skull.

Craniotomy - surgical opening of the skull to gain access to the intracranial structures.

Crepitus - grinding noise or sensation within a joint.

Crown - a "cap" that covers a cracked or broken tooth, unfixed by a filling, to approximate its normal size and shape.

Cryoprostatectomy - freezing of the prostate through the use of liquid nitrogen probes guided by transrectal ultrasound of the prostate.

Cryothalamotomy - a surgical procedure in which a supercooled probe is inserted into a part of the brain called the thalamus in order to stop tremors.

Cryptosporidia - parasite that can cause gastrointestinal infection and diarrhea. (See also gastroenteritis.)

Cued speech - method of communication that combines speech reading with a system of handshapes placed near the mouth to help deaf or hard-of-hearing individuals differentiate words that look similar on the lips.

Cupping - the use of warmed glass jars to create suction on certain points of the body.

Cyanosis - bluish color in the skin due to insufficient oxygen levels in the blood.

Cyclic vomiting syndrome (CVS) - sudden, repeated attacks of severe vomiting (especially in children), nausea, and physical exhaustion with no apparent cause.

Cystic duct - tube that carries bile from the gallbladder into the common bile duct and the small intestine.

Cystic duct obstruction - blockage of the cystic duct, often caused by gallstones.

Cystometry - diagnostic procedure that measures bladder capacity and pressure changes as the bladder fills and empties.

Cystourethrocele - condition that results when the urethra and its supporting tissues weaken and drop into the vagina leading to stress incontinence.

Cytology - the study of individual cells.

Cytomegalovirus (congenital) - one group of herpes viruses that infect humans and can cause a variety of clinical symptoms including deafness or hearing impairment; infection with the virus may be either before or after birth.