Skip to Main Content

Welcome to

Together is a new resource for anyone affected by pediatric cancer - patients and their parents, family members, and friends.

Learn More

Glossary - O


Showing 1-25 out of 25 Terms

We're sorry, it looks like there has been an error. Please try again soon.

  • Obesity


    A condition marked by an abnormally high, unhealthy amount of body fat.

  • Observation


    In medicine, watching a patients condition but not giving treatment unless symptoms appear or change.

  • Occupational therapist

    (AH-kyoo-PAY-shuh-nul THAYR-uh-pist)

    A health professional trained to help people who are ill or disabled learn to manage their daily activities.

  • Ommaya reservoir

    (oh-MY-uh REH-zer-vwahr)

    A device surgically placed under the scalp and used to deliver anticancer drugs to the fluid surrounding the brain and spinal cord.

  • Oncologist


    A doctor who has special training in diagnosing and treating cancer. Some oncologists specialize in a particular type of cancer treatment. For example, a radiation oncologist specializes in treating cancer with radiation.

  • Oncology


    A branch of medicine that specializes in the diagnosis and treatment of cancer.

  • Operating room

    Surgical site.

  • Ophthalmologist


    A doctor who has special training in diagnosing and treating eye problems, including injury and disease.

  • Opioid


    A substance used to treat moderate to severe pain. Opioids are like opiates, such as morphine and codeine, but are not made from opium. Opioids bind to opioid receptors in the central nervous system. Opioids used to be called narcotics. An opioid is a type of alkaloid.

  • Optic nerve

    (OP-tik nerv)

    The nerve that carries messages from the retina to the brain.

  • Optical

    Pertaining to the sense of sight or to the eyes.

  • Organ


    A part of the body that performs a specific function. For example, the heart is an organ. organelle.

  • Organism


    A living thing, such as an animal, a plant, a bacterium, or a fungus.

  • Orgasm


    The final part of the sex act, which involves contraction of sexual organs and a sudden release of endorphins, leading to a feeling of pleasure. In males, orgasm usually occurs with release of semen.

  • Orthopedic surgeon

    (OR-thuh-PEE-dik SER-jun)

    A surgeon who has special training in diagnosing and treating injuries and diseases of the musculoskeletal system. This includes the bones, joints, tendons, ligaments, and muscles.

  • Osteomyelitis

    Inflammation of the bone caused by an infection, which may spread to the bone marrow and tissues near the bone. Osteomyelitis can cause severe pain in the infected bone. If it is not treated, it can kill bone tissue.

  • Osteoporosis


    A condition in which there is a decrease in the amount and thickness of bone tissue. This causes the bones to become weak and break more easily. Osteoporosis may be caused by older age, hormone changes, taking certain medicines, and not eating enough foods with calcium and vitamin D. It may also be caused by certain types of cancer and cancer treatment.

  • Osteosarcoma


    A cancer of the bone that usually affects the large bones of the arm or leg. It occurs most commonly in young people and affects more males than females. Also called osteogenic sarcoma.

  • Otic

    Relating to the ear.

  • Otitis

    Ear infection.

  • Ovaries


    A pair of female glands in which the eggs form and the female hormones estrogen and progesterone are made. These hormones play an important role in female traits, such as breast development, body shape, and body hair. They are also involved in the menstrual cycle, fertility, and pregnancy. There is one ovary on each side of the uterus.

  • Over-the-counter


    Refers to a medicine that can be bought without a prescription (doctor's order). Examples include analgesics (pain relievers), such as aspirin and acetaminophen. Also called nonprescription and OTC.

  • Ovulation


    The release of an egg from an ovary during the menstrual cycle.

  • Oxygen


    A colorless, odorless gas. It is needed for animal and plant life. Oxygen that is breathed in enters the blood from the lungs and travels to the tissues.

  • Oxygen mask

    An implement to enable breathing.