Online Medical Dictionary

Letter A

Prefix derived from the Greek meaning of not.
Abbreviation used on prescriptions of the Latin ante cibum, meaning before meals. Other Latin abbreviations traditionally used in writing prescriptions include:
  • b.i.d. = bis in die, twice a day
  • gtt. = guttae, drops
  • p.c. = post cibum, after meals
  • p.o. = per os, by mouth (take orally)
  • p.r.n. = pro re nata, as needed
  • q.d. = quaque die, once per day
  • q.i.d. = quater in die, four times per day
  • q.# h.: quaque, every indicated number of hours
  • q.h. = every hour
  • t.i.d. = ter in die, three times per day
  • ut dict. = ut dictum, as directed
Abdominal aortic aneurysm.
The American Association for the Advancement of Science.
Ass Am Medical Colleges(AAMC)
The American Association of Medical Colleges, a not-for-profit association composed of the 16 accredited medical schools in Canada; the 125 accredited medical schools in the United States; more than 400 teaching hospitals and health systems; 90 academic and professional societies; and medical students and residents. The AAMC mandates to improve health services through the advancement of academic medicine, the strengthening of quality medical education and training, and the integration of education into the provision of effective health care. The AAMC also provides the Medical College Admission Test (MCAT) required of all applying to medical schools in Canada or the U.S.
The symbol for the enzyme arylalkylamine N-acetyltransferase, member of the super-family of acetyltransferase enzymes, and the gene encoding it. AANAT is only present in animals, bacteria and yeast. AANAT is used to produce melatonin, a hormone that regulates the cycles of sleep and waking.
  1. Alert and oriented
  2. American Association of Ophthalmology
  3. American Academy of Otolaryngology
  4. American Association of Orthodontists
  5. The enzyme amino acid oxidase
Aarskog-Scott Syndrome
Syndrome yielding ocular widely spaced eyes, front-facing nostrils, a broad top lip, a malformed scrotum, and laxity of the ligaments, which can result in the bending back of knees, flat feet and fingers that can over-extend.
Aase-Smith Syndrome I
A congenital malformation syndrome characterized by hydrocephalus (abnormal amount of fluids in the cavities of the brain), cleft palate, and severe joint contracture.
Aase-Smith Syndrome II
A genetic disorder sometimes detected early in infancy, characterized by the presence of a third bone in the thumbs and abnormally reduced production of red blood cells. Though cause is unknown, it is believed that the disorder is inherited through a recessive autosomal trait.
Ab ovo
From Latin meaningfrom the beginning or from the egg.
Prefix meaning "away from" derived from Latin.
To decrease or make less.
A decrease or easing, usually referring to an abatement of pain or symptom.
ABCD Rating
A system giving stages for prostate cancer.
The part of the body located between the chest and pelvis, including the stomach, small intestine, rectum, liver, spleen, pancreas, colon, kidneys, appendix, bladder and gallbladder organs.
Abdominal Aneurysm
An aneurysm occurring within the abdomen.
Abdominal Aorta
Beginning at the diaphragm, the abdominal aorta continues from the thoracic aorta to run down to the end point of the aorta, where it splits to form the iliac arteries. The abdominal aorta supplies oxygenated blood to the abdominal and pelvic organs and to the legs.
Abdominal Aortic Aneurysm
A ballooning of the main artery (the aorta) as it courses to the abdomen.
Abdominal Cavity
The space between the abdominal wall and the spine, containing the lower part of the esophagus, stomach, small intestine, rectum, liver, gallbladder, pancreas, spleen, kidneys, colon and bladder.
Abdominal Guarding
The abdominal wall muscles reaction to tense, or go into spasm, to guard inflamed organs within the abdomen from any pressure put on them. Tensing can be detected by pressing the abdomen wall.
Abdominal Hysterectomy
Surgical removal of the uterus through an incision made in the wall of the abdominal wall.
Abdominal Pain
Pain in the abdomen resulting from varying prompters dependent on condition, gender and age.
The movement of a limb away from the body.
Abductor muscle
Any muscle used to pull a body part away from the body.
Deviation or irregularity.
Arterial Blood Gas(ABG)
Sampling blood to check levels of oxygen and carbon dioxide in the arteries.
Not living.
Loss of function with unknown reason.
To remove, such as in a tumor.
Not of the norm or usual structure.
ABO Blood Group
The human blood group system.
Something causing the premature end to a pregnancy.
The premature end of a pregnancy.
A sudden breaking off or away, such as in a placenta from the uterus wall; abruptio placentae.
Slang reference to abdominal muscles.
A local accumulation of puss in the body.
The removal of tissue by surgical process.
Absent Eye
Anophthalmia, a congenital malformation.
Frequent absence from job or other duty without validity in reason.
Illustrating restraint in food or alcohol consumption.
Self-denial of food, drink or sex made voluntarily.
Abuse of a Child
Abuse of a child including neglect, physical and emotional abuse, and sexual abuse.
Abuse of Pregnant Women
Abuse of a pregnant woman, most often perpetrated by the woman's spouse, partner or family member. May be associated with lower than normal birth weight.
Abused Inhalant
A chemical vapor inhaled in excess for misappropriated use. Includes solvents, gases and nitrates. Chronic abuse can cause severe, long-term damage to the brain, liver and kidneys.
Abbreviation for ante cibum on a prescription; acromioclavicular (shoulder joint); and antecubital (crook of elbow).
AC Joint
Acromioclavicular joint located between the shoulder and the collar bone.
Having less than normal levels of carbon dioxide in the blood.
Adenoid cystic carcinoma.
Acceptable Daily Intake (ADI)
Estimate of the amount of a consumable substance, expressed in relation to body mass, which can be ingested each day over an average lifetime without causing health risk.
The opportunity to receive health care.
Accessibility of Services
The ability to receive medical care and health services when required.
Accessory Placenta
A placenta existing in addition to and separate from the main placenta. Also referred to as a succenturiate or supernumerary placenta.
Acclimatization to Altitude
Adapting to the decrease in oxygen concentration along specific altitudes.
Male obstetrician in French.
A female obstetrician in French.
Not composed of cells.
Pain reliever and fever reducer, composing Tylenol.
Acetylsalicylic Acid
Composing Asprin.
Achilles Tendon
The sinew attaching the calf muscle to the heel bone.
Achilles Tendonitis
Inflammation of the Achilles tendon.
Digestive fluids of the stomach lacking in hydrochloric acid.
Achoo Syndrome
A disorder marked by paroxysms of sneezing provoked by the sudden exposure to intensely bright light. Also called the photic sneeze reflex or the helio-ophthalmic outburst syndrome.
Hereditary sight disorder caused by a lack of cones.
Acid Indigestion
Excessive secretion of hydrochloric acid by stomach cells. Known as hyperchlorhydria and heartburn.
Acid Reflux
Condition in which stomach acid rises into the esophagus.
Acne Vulgaris
Acne resulting from overactive oil glands which become plugged, red and inflamed.
Inherited disorder that causes abnormalities of the skull, face, hands and feet.
Blueness of the hands and feet caused constriction of small arterioles located at the ends of the arms and legs.
Pain in the hands and feet.
An abnormal and persistent fear of heights.
Activated Charcoal
Charcoal heated to increase its absorptive capacity, sold over-the-counter to help relieve intestinal gas. Can also absorb or neutralize swallowed poisons and purify liquids.
The applying of pressure on specific body points to control or manage symptoms such as pain, headaches or nausea.
The insertion of needles into specific body points to reduce or manage pain.
A person trained and capable in the practice of acupuncture.
An abrupt onset of a condition or disease.
Acute Abdomen
Abrupt onset of pain in the abdomen.
Acute Brain Syndrome
Acute Confusional State
Acute Illness
A disease or condition with a quick and sudden onset and, usually, a short duration.
Acute Leukemia
Cancer of the white blood cells that emerges abruptly and, if not treated, progresses quickly. The two major forms of acute leukemia are acute lymphoblastic leukemia (ALL) and acute myelocytic leukemia (AML).
Acute Mountain Sickness (AMS)
The effect of being located at a high altitude.
Acute Pain
Pain that comes on rapidly and can be severe. Differed to chronic pain.
Latin prefix meaning toward.
Adam's Apple
An anatomic feature located in the front of the male neck, formed by the protrusion of thyroid cartilage.
Adapter Protein
Protein acting as a connecting molecule.
Abbreviation for Attention Deficit Disorder.
The movement of a limb toward the body.
Adductor Muscle
Any muscle that pulls a body part toward the body.
The inflammation of a gland.
The Latin word to refer to appendages.
Adrenal Cortex
The outer portion of the adrenal gland located on the kidneys.
Adrenal Failure
Condition arising when the adrenal glands fail to produce sufficient amounts of the adrenal hormones needed to maintain rudimentary levels such as blood pressure.
Adverse Effect
A negative or abnormal result. Can be caused by administration of medication or exposure to a chemical.
Adverse Reaction
An unexpected or negative reaction to a prescription.
Swallowing too much air. A common cause of accumulated gas in the stomach.
An abnormal and persistent fear of flying or of air.
Sinus troubles resulting from changing atmospheric pressures. Also termed barosinusitis or sinus barotrauma.
Aerospace Medicine
Medicine concerned with the maintenance of health, safety and the performance of those employed in aviation and space travel.
Middle ear problems caused from changing atmospheric pressures.
African Tapeworm
The beef tapeworm most common of large tapeworms that can be consumed and grow in the intestines of a human.
The placenta and fetal membranes expelled from the uterus after the baby has been delivered.
Age-related Macular Degeneration
An eye disease usually occurring among people over age 60 that progressively destroys the central portion of the retina.
Lack of development, or the failure to form.
Quck growing, with a tendency to spread rapidly.
The process of becoming older, as is genetically determined and modulated by environment.
Heartburn, acid indigestion, upset stomach or, a general feeling of upset.
Of the the father's side.
The inability to recognize things or persons despite knowing the characteristics of those items or persons.
An abnormal and persistent fear of public places or open areas.
Fever marked by chill spasms, fever and sweating.
Abnormal and persistent fear of crossing any roadway.
Acronym for Acquired Immunodeficiency Syndrome.
AIDS Dementia Complex
A brain disorder that occurs in AIDS patients, causing the cognitive loss and affecting the ability to normally function in a social or occupational environment.
AIDS Wasting Syndrome
Involuntary weight loss of 10 per cent of the baseline body weight for the individual, coupled with either chronic diarrhea or chronic weakness and documented fever of 30 days or more, intermittent or constant, in the absence of a concurrent condition other than HIV that would account for the symptoms.
An abnormal and persistent fear of felines.
Airway Obstruction
Partial or complete blockage, caused by allergens or various other prompters, of the airways to the lungs.
Impaired or poverty of body movement.
Without movement. A term used in neurology to describe a patient in coma.
A non-essential amino acid, and one of the 20 building blocks of protein.
Genetic disorders in which partial or total lack of the pigment melanin is present in the eyes, skin, and hair.
Alcohol Abuse
Use of alcoholic beverages to excess, on occasion or with regularity.
Alcohol Poisoning
A condition resulting from the consuming of a toxic amount of alcohol. Can be fatal if emergency treatment is not sought.
Physical dependence on alcohol.
Alexander Disease
A slowly progressing and fatal brain disorder most commonly occurring in children.
Alexander Technique
A technique employed to teach patients how to properly coordinate the body and mind to release tension and improve posture, coordination and overall health.
A neurological disorder characterized by loss of the ability to read or understand written text.
An abnormal, in excess of normal, and persistent fear of pain.
Alice in Wonderland Syndrome
A syndrome of wherein the patient views their surrounding space, time, or body parts as altered. Often occurs in patients with a familial history of migraine suffering.
Alien Hand Syndrome
The feeling that one's hand is not in one's control. Various types of brain injury may cause subtypes of alien hand syndrome.
A foreign substance that may cause a reaction in people whose bodies cannot accept them.
Allergic Reaction
The immune system's hypersensitive response to a substance to which it is allergic.
Allergy Skin Test
Test conducted on the skin of a patient to identify if the patient is allergic, or shows reaction, to applied allergens.
Total inability to speak, as in profound mental retardation or advanced dementia. Synonymous with aphasia.
Alopecia Areata
Patchy baldness.
Alopecia Universalis
The absence of all body hair.
Altitude Illness or Sickness
Disorder caused from journeying to a high altitude, most commonly occurring at heights above 2,440 meters, caused by differing oxygen concentration.
Tiny air sacs located within the lungs where the exchange of oxygen and carbon dioxide ocurrs.
Inflammation of the alveoli.
Alzheimer's Disease
A progressive neurologic disease, caused by degenerated cortical areas of the brain, leading to the irreversible loss of neurons. Alzheimer's disease is marked by dementia; a growing impairment in memory, judgment, decision making, orientation to surroundings, and speech.
Abnormal and persistent fear of dust.
Condition wherein the nipple is present but breast tissue is absent, often a result of radiation or surgery.
Ability to use the right and left hands with equal dexterity.
Ambiguous Genitalia
Genitalia neither typical of female nor male genitalia.
The absence or cessation of menstruation, either from birth or after puberty.
Amino Acid
One of the 20 building blocks of protein, the function of which is determined by the genetic code of the DNA.
Inability to remember. May be brought on by trauma, head injury or other circumstances.
Prenatal diagnosis procedure, wherein amniotic fluids are attained from which to conduct genetic and other diagnostic tests.
The thin membrane surrounding the fetus during pregnancy.
The removal of amniotic fluid through amniocentesis.
Amniotic Fluid
The fluid surrounding and protecting the fetus from pressure.
A single-celled organism constantly changing shape.
An antibiotic of the penicillin family effective against various bacterias such as Pneumococci, Neisseria gonorrhoea, Escherichia coli, Haemophilus influenzae, Streptococci, and strains of Staphylococci. Also used in the treatment of urinary tract infections and gonorrhea.
A drug baring a stimulant effect on the central nervous system, with potential to become addictive.
Term for both the amygdaloid nucleus in the brain and the tonsils termed so for their almond-like shape.
Anal Fissure
Common tear in the anal canal and cause of blood to appear in the stool.
A drug or medicine prescribed for pain reduction, that does not result in loss of consciousness.
Processes used to gain understanding of complexities.
Inability to feel sensation through touch. Such a person is stated to be anaptic.
Anaphylactic Shock
A widespread, intense allergic reaction marked by dizziness, loss of consciousness, difficulties breathing, tongue swelling, blueness colouring of skin, and low blood pressure, requiring immediate emergency treatment.
The restorative science and art of prosthesis, or forming malformed or absent body parts by artificial means.
The physiology of the human form.
A male sex hormone that promotes the development and maintenance of the male sex characteristics, the dominant of which is testosterone.
The development of characteristics typically male.
Branch of medicine regarded to men's health, including infertility and sexual dysfunction. Countered by gynecology for women.
An abnormal and persistent fear of men.
Having fewer than normal numbers of red blood cells or hemoglobin in the blood.
A medical professional specialized in the practice of anesthesiology, utilizing agents to induce insensibility to pain.
Branch of medicine focussed in the use agents to induce insensibility to pain.
A substance inducing lack of feeling or awareness. Local anesthetic induces loss of feeling in a concentrated part of the body.
A localized dilatation of an artery or vein.Angina
Chest pain resulting from an inadequate supply of oxygen to the muscle of the heart. Angina pain is usually severe, causing a crushing and suffocating sensation.
A procedure in which blood vessels are injected with a radioopaque dye which outlines them on x-ray for viewing. TUsed to observe arteries in senveral areas of the body, including the brain, neck, aorta, chest, heart, pulmonary circuit, kidneys and limbs.
Disease of the arteries, veins and capillaries.
Procedure that utilizes a balloon-tipped catheter to enlarge narrowing observed in a coronary artery.
Loss of the ability to experience or take pleasure in activities as one could.
Anorexia Nervosa
Eating disorder marked by drastically reduced appetite or total aversion to eating. A complex and potentially fatal psychological disorder.
Lacking the sense of smell.
Anovular Menstruation
Menstruation without ovulation. The ova does not exit the overy, most often disintegrating, but if fertilized results in a dangerous pregnancy within the ovary.
An agent that acts against and/or blocks an action.
Anything that acts to destroy bacteria or suppress ability for bacteria to grow or to reproduce.
Medication used to treat infections induced by bacteria or other microorganisms.
Antibiotic resistance
A bacteria or other microorganisms' ability to withstand an antibiotic to which they were once affected by. Also termed drug resistant.
A specialized immune protein, produced when an antigen is introduced to the body, possessing the fascinating ability to combine with the antigen that triggered its making and render it benign.
Any medication or treatment used to prevent or aid patients suffering from depression.These include selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors, tricyclics and tetracyclics.
An agent that counteracts a poison, neutralizing its negative effects.
A substance used to treat infections of the fungal variety.
A substance capable of inciting an antibody's production.
Any medication or treatment believed to be effective in the treatment of psychosis.
A substance that reduces fever.
Feelings of apprehension and fear, marked by palpitations, sweating, and stress.
The body's largest artery, rising from the left ventricle of the heart, ascending, arching and descending through the chest and abdomen to end in a division of the two common illiac arteries, which extend to the legs.
The inability to consume victuals.
A disorder in which expression or comprehension by speech, writing, or signs is lost or defected.
A moment of time during which breathing ceases or is reduced markedly. The two types of apneas are obstructive sleep apnea and central sleep apnea.
Surgical removal of the appendix, usually performed when the appendix wall is inflamed.
Inflammation of the appendix, the worm-like projection emerging from the first section of the colon. Appendicitis is usually incited by a bacterial infection of the appendix and can progress to produce a puss-filled abscess or peritonitis.
The small, worm-like outpouching emerging from the beginning of the ascending colon.
Appendix Cancer
Cancer of the appendix, incited by malignant cells or tumors.
Approved Drug
A medication approved for sale and marketing.
The inability to perform a voluntary motor movement despite the demonstrative ability to possess normal muscle function. Caused by a discrepancy in the cortex of the brain.
An abnormal and persistent fear of water.
Argon Laser
A laser used in ophthalmology for photocoagulation.
An alternative and complimentary therapy utilizing concentrated scents extracted from flora, rind, roots etc. believed to possess healing properties.
Abnormal heart rhythm.
A vessel carrying oxygen-rich blood away from the heart to the body's furthest reaches.
Joint inflammation, of which there are more than 100 forms.
Artificial Abortion
An abortion proceeded upon intentionally. Also termed an induced or therapeutic abortion, not a spontaneous abortion or miscarriage.
Artificial Heart
A human-made heart.
Artificial insemination
A procedure in which a male's sperm is deposited into a woman's uterus through a catheter inserted through her cervix, in an attempt to conceive.
Artificial Knee
A human-made knee replacement, placed with a metal shell onto the end of the femur.
Artificial Pacemaker
A device implanted into the body which uses electrical impulses to regulate and mimic the heart's natural rhythm.
Artificial Pancreas
A machine which measures and maintains blood glucose levels by release of insulin, mimicking the function of the pancreas.
Asperger Syndrome
An autistic, developmental disorder marked by an inability to comprehend appropriate social behaviour.
Breathing that has become impaired or impeded.
Assistive Technology
Electronic, computerized or otherwise built devices which aid a disabled person to perform necessary functions with greater ease.
A common condition in which various triggers, such as allergens, sport or infection, cause the bronchi to swell, narrowing the asthmatic person's airways, though the alveoli and lung tissue remain unaffected. Corrected and treated by use of prescribed inhaler, and in many cases often subsides with age.
Having no symptoms.
Asymptomatic Infection
An inapparent infection, where the no symptoms are visible.
A procedure in which plaque is removed from an artery, where it as built up from an accumulation of cholesterol and other such substances.
Athlete's Foot
An infection of the skin caused by the fungus Trichophyton, spurred when the upper skin is left moist and warm.
Without a thymus gland.
The wasting away of muscle mass, as prompted by malnutrition, lack of mobility or muscular illness.
A grouping of neuropsychiatric disorders marked by abnormal and repetitive behaviours and a lack in social interaction and communication skills. In some cases the autistic individual is completely non-verbal. Autism is usually detected within a child's first six years.
Autoimmune Disease
Condition causing the immune system to attack its own body tissues, more common in women, as is believed to be influenced by the hormone estrogen. Individuals with autoimmune diseases are often found to host an abnormal mass of antibodies circulating in their blood.
An unconscious movement often resembling a tic, or may be manifested in a complex sequence of normal-appearing movements. Automatic behaviour is seen in several differeny neurological and psychiatric disorders.
An abnormal and persistent fear of solitude and loneliness.
Postmortem examination; necropsy.
Autosomal Chromosome
Any chromosome excluding the sex chromosomes. Humans are built of 44 autosomes, or 22 autosomal chromosome pairs in the nuclei of each cell, in addition to the sex chomosomes, XY for males and XX for females, equating 46 autosomes total.
See Autosomal Chromosome.
The transplanting of tissue from one part of an individual's body to another.
AV Node
An electrical relay station located between the atria and the lower heart chambers.
Avian Influenza
Commonly referred to as the avian flu or the bird flu, this contagious viral disease, spurred by influenza A virus and subtypes, can cause to 100 per cent mortality among domestic fowl, most commonly effecting chickens and turkeys and, very minimally, humans.
A long, projection of the neuron, or nerve cell, the axon acts as a message carrier, transmitting the electrical impulses emitted by the neuron from the cell body through to the target cells.