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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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…
optical

Having to do with vision.
optometry

The practice of eye and vision care.

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