Abrasion
A superficial scrape of the skin.

Abscess
A walled-off infection containing pus; usually associated with local pain, warmth, swelling and/or redness; may need to be cut open and allowed to drain.

Adenoiditis
Inflammation of the lymph tissue found in the back of the throat, above the tonsils; usually caused by an infection.

ADHD
Attention deficit hyperactivity disorder; attention deficit disorder (ADD); hyperactivity.

AIDS
Acquired immunodeficiency syndrome; marked by inability of the immune system to function properly in protecting the body from disease; caused by human immunodeficiency virus (HIV); treatment is available.

Allergen
A substance that triggers an allergic reaction.

Allergic rhinitis
A runny, stuffy nose resulting from inflammation of the inside lining (mucous membranes) of the nose; caused by allergies.

Allergy
A condition in which the body is especially sensitive to certain substances (allergens); symptoms include sneezing, runny nose, watery eyes, wheezing, itching and/or rashes and swelling; serious allergic reactions may be life-threatening.

Alopecia
Baldness; loss of hair.

Amblyopia
Poor, dim vision despite a normal eye; caused by abnormal development of areas in the brain that control vision; in children often caused by a wandering eye that did not focus sharply during the early years of life.

Amenorrhea
The absence of menstrual periods.

Anemia
Any condition in which there is decrease in the number of red blood cells in the circulatory system, or a reduction in the pigment in red cells that carries oxygen (hemoglobin); symptoms include tiredness, fast heart rate, heart murmurs, shortness of breath, and paleness of the skin and mucous membranes; common causes include blood loss, iron deficiency and hereditary disorders like sickle cell anemia; treatment varies depending on the cause.

Anorexia nervosa
A psychological eating disorder marked by an abnormal fear of obesity, a distorted body image, and deliberate (and sometimes life-threatening) weight loss caused by reduced food intake; typically seen in adolescent girls.

Antibiotic
Usually refers to a type of medication, such as amoxicillin, that inhibits the growth of, or kills, bacteria. (Note: Terms like "antibacterial," "antiviral," and "antifungal" are more accurate and specific names for medications that fight bacteria, viruses and fungi, respectively).

Apgar score
A score from 0 to 10 that reflects a newborn's well-being immediately after delivery; the total is the sum of ratings from 0 to 2 for the infant's heart rate, breathing effort, muscle tone, responsiveness, and skin color at 1, 5, and 10 minutes after delivery; a perfect score of 10 is rarely seen; scores less than 6 are considered low.

Apnea
Absence of breathing.

Arteriosclerosis
A condition marked by the hardening of the arteries.

Artery
A blood vessel that carries blood away from the heart and delivers oxygen to the tissues.

Arthritis
Inflammation of the joints; often associated with pain, swelling and difficulty moving.

Artificial ventilation
Artificial respiration; an assisted form of breathing; a part of cardiopulmonary resuscitation (CPR) where air is forced into the victim's breathing passages by another person or by a bag-and-mask apparatus.

Asphyxia
Suffocation; impaired or absent ability to breathe in enough oxygen and breathe out enough carbon dioxide.

Aspiration
Breathing liquid or solid substances into the airway.

Asthma
Reactive airway disease; a chronic condition of the lungs marked by recurrent wheezing, coughing, difficulty breathing and production of thick mucus; the cause is not known but suggested causes include drugs, food allergies, exercise, infection, stress and exposure to environmental triggers like smoke or allergens.

Athlete's foot
An infection of the feet caused by a fungus; usually marked by tenderness, itching, a persistent foul odor, redness and peeling of the skin between the toes and on the soles of the feet; responds to treatment with antifungal medications.

Autism
A neurological condition marked by disordered language and relationships with people; often characterized by decreased ability to interact socially; occurs on a spectrum ranging from mild to severe.

Autoimmune disease
A condition characterized by the immune system's turning against a person's own body tissues because it recognizes those tissues as foreign; the attack by the immune system can cause serious damage to those tissues; treatment varies depending on the condition.

B

Bacteremia
The presence of bacteria in the bloodstream.

Bacteria
Tiny one-celled organisms that can be seen only with a microscope; can cause infections ranging from mild to severe; usually respond well to treatment with antibiotics.

Birthmark
A mole or blemish of the skin that is present from birth.

Boil
Furuncle; a localized, painful pus-filled infection of the skin (or abscess), starting in a hair follicle; caused by bacterial infection, usually staphylococcus.

Bronchiolitis
Inflammation of the small airways (bronchioles); characterized by wheezing and/or difficulty breathing; usually caused by a viral infection.

Bronchitis
Inflammation of the large airways or bronchial tubes; often characterized by cough; can be caused by a viral or bacterial infection.

Bronchopulmonary dysplasia (BPD)
A condition of some premature infants in which there is scarring, chronic swelling and inflammation of the lungs; may improve as the infant grows and new lung tissue is formed.

Bulimia
A psychological eating disorder marked by periods of binge eating followed by self-induced vomiting or purging.

C

Cancer
A term used to describe abnormal growths of cells that are malignant because they can invade surrounding tissues, and they have the ability to travel and take root at other sites in the body (metastasize).

Candida (Candida albicans)
A very common yeastlike fungus that causes diaper rash and mouth infections (thrush); frequently seen in infants.

Canker sore
An ulceration on the inside lining of the mouth; the cause is usually unknown.

Cardiopulmonary resuscitation (CPR)
An emergency measure taken to maintain blood flow to the brain following a cardiac arrest or absence of breathing; uses artificial ventilation and chest compressions.

Cellulitis
Inflammation of the tissue just below the skin; usually marked by localized pain and redness; ordinarily caused by infection, but has a variety of causes including chemical irritation.

Cerebral palsy
A neurologic condition marked by varying degrees of impairment in the use of muscles, resulting in abnormal movement and posture; not a progressive disease; can be caused by brain damage, usually before birth or during delivery, but in some cases the cause is unknown.

Chickenpox
A very contagious vaccine-preventable viral infection marked by fever and an itchy vesicular rash (small blisters on a red base); caused by the varicella-zoster virus; can be prevented with varicella vaccine.

Chlamydia (Chlamydia trachomatis)
Bacteria that cause one of the most common sexually transmitted diseases; also can cause pneumonia and conjunctivitis in infants; responds to treatment with antibiotics.

Circumcision
The removal of the foreskin of the penis.

Cleft lip, cleft palate
A congenital fissure (split) in the lip and/or the roof of the mouth; typically is the result of incomplete union of these areas during embryonic development; can occur randomly or run in families.

Clubfoot
Talipes equinovarus; a congenital deformity of the foot marked by twisting in of the ankle, heel and toes.

Cold
A viral infection of the upper respiratory tract marked by runny nose, sneezing, sore throat and cough; does not require, or respond to, antibiotics.

Cold sore
Fever blister; a small blister on the lips or next to the lips; caused by the herpes simplex virus.

Colitis
Inflammation of the colon; the cause may be infectious, but often is unknown.

Colostrum
Thin, milky, yellowish fluid which is full of protein, antibodies and minerals, but low in carbohydrates and fat; secreted by the glands in the breast during pregnancy and after delivery until the more mature milk comes in.

Coma
A state of unconsciousness from which the person cannot be aroused; may be caused by trauma, poisoning or a variety of other factors including infection.

Concussion
Temporary impairment of consciousness with loss of responsiveness and awareness; may also be accompanied by changes in vision or balance, and loss of memory for the traumatic event; lasts for seconds to hours after a head injury; usually caused by sudden trauma to the head.

Congenital
Existing at or before birth; may be caused by environmental or hereditary (genetic) influences, or the cause may be unknown.

Congestive heart failure
Inability of the heart to pump sufficient blood to meet the body's demands; causes a backing-up of the blood circulation leading to swelling in the body, weakness and shortness of breath.

Conjunctivitis
Inflammation of the membrane that covers the white of the eye and the lining inside the eyelids; results in redness and irritation, with or without discharge from the eye; typically caused by extreme heat, cold or chemicals, but can be caused by viral or bacterial infections, or by allergies; when caused by a contagious infection like adenovirus, is known as "pinkeye."

Constipation
Infrequency or difficulty in passing bowel movements, often because of uncomfortably hard stools.

Convulsion
Seizure; sudden involuntary jerking of the muscles; caused by an abnormal electrical discharge in the brain.

Cradle cap
Seborrhea; greasy, scaly yellowish crust on the scalp; can also cause rash and irritation of the face and groin; caused by excess production of oils.

Craniosynostosis
Premature closure of the open spaces between the bones of the skull; if left untreated, can lead to abnormal head shape and growth.

Cyanosis
Bluish or purplish skin color; caused by reduced oxygen in the blood.

Cyst
An abnormal sac that commonly contains fluid, but can also can contain air or other material.

Cystic fibrosis
A hereditary disease that causes a wide variety of serious problems including severe lung disease, abnormal digestion and poor growth.

Cystitis
Inflammation of the bladder; generally caused by a viral or bacterial infection or chemical irritation.