Dictionary

Enter a word or phrase below to search our online dictionary of over 1,300 general medical terms, or click on a letter of the alphabet to view all terms beginning with that letter:

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Phrase Definition
obesity Having too much body fat. A weight more than 20% above the normal range.
obsession An ongoing preoccupation with an idea.
obsessive-compulsive Marked by a need to repeatedly perform certain behaviors or rituals.
obstetrics The branch of medicine that deals with the care and treatment of women during pregnancy and childbirth.
occiput The back of the head.
occult Hidden from view.
occupational illness Any illness caused or aggravated by a person's job.
occupational therapy Teaching useful skills to sick or handicapped people to promote rehabilitation and healing.
ocular Having to do with the eye.
odontalgia Toothache.
olecranon The projection of the ulna (the larger of the two bones in the forearm) at the elbow.
olfactory Having to do with the sense of smell.
oligomenorrhea Light menstrual flow.
oligospermia A low number of sperm in the semen.
oliguria A condition characterized by an abnormally small output of urine.
oncology The study of tumors.
oophorectomy The surgical removal of an ovary.
ophthalmology The branch of medicine that pertains to the eye and its diseases.
optic neuritis Inflammation of the optic nerve, which connects the eye to the brain. Symptoms include pain with eye movement, blurred vision and sometimes temporary blindness.
optical Having to do with vision.
optometry The practice of eye and vision care.
orbit The bony cavity containing the eyeball. Eye socket.
orchiectomy The surgical removal of one or both testicles. Also called castration.
organ A structural unit of an animal or plant that serves a specific function.
organic Having to do with substances derived from living organisms.
orgasm Sexual climax.
orifice The entrance or outlet of a body cavity.
oropharynx The part of the pharynx behind the mouth and tongue.
orthodontics The branch of dentistry that deals with the correction of irregularities of the teeth and related facial problems.
orthopedics The branch of medicine that deals with the treatment of deformities, diseases and injuries of the bones, joints and muscles.
orthopnea Difficulty breathing when lying flat.
oscillation A back-and-forth motion; vibration.
Osgood-Schlatter disease Inflammation of the bone and cartilage of the shin bone, just below the knee.
ossicle A small bone.
osteoarthritis A slowly progressive form of arthritis, usually found in older people. Characterized by deterioration of bone cartilage.
osteoma A bony tumor.
osteomalacia Softening of the bones resulting from deficient bone calcium.
osteomyelitis Infection of a bone.
osteopathy A system of therapy emphasizing primary medical care and the importance of body mechanics and manipulation to correct abnormalities.
osteoporosis A bone disorder characterized by a reduction in bone density, chiefly found in women who have passed menopause and the elderly.
ostomy A procedure done to make a passageway for waste. A colostomy is an example.
otic Having to do with the ear.
otitis Inflammation of the ear. Otitis externa (inflammation of the ear canal) is also called swimmer's ear, while otitis media is a middle-ear infection.
ovary The female sex gland that contains ova, or eggs.
ovulation The process in which an ovum is released from the ovary.
ovum Egg; the female reproductive element.
oximeter A device for determining the oxygen saturation level of the blood.
oxygen A chemical element essential for sustaining life.
oxytocin A pituitary hormone that encourages the pregnant uterus to contract and is sometimes used to induce labor. It also encourages milk to be expressed during breastfeeding.