Dictionary of Medical Terms

Gain a better understanding of medical terminology by searching our dictionary of more than 1,300 terms.

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All terms that start with the letter O

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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…
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…
ostomy

A procedure done to make a passageway for waste. A colostomy is an example.
otic

Having to do with the ear.