Oncogene   
A heredity unit that controls the growth of cancer cells.

Oncologist   
A doctor who specializes in the diagnosis and treatment of cancer.

Oncology   
The study and treatment of cancer. Doctors who specialize in oncology are called oncologists.

Oncology Certified Nurse   (OCN)
A registered nurse who has met requirements and successfully completed a certification exam.

Oncology Clinical Nurse Specialist   
A registered nurse with a masters degree who specializes in the education and treatment of cancer patients.

Oophorectomy    
Surgical removal of one (unilateral) or both (bilateral) diseased ovaries.