The branch of medicine that deals with tumors, including study of their development, diagnosis, treatment, and prevention.
肿瘤学研究肿瘤的医学分支，他的研究包括其发展、诊断、治疗和预防
The branch of dentistry that deals with the diagnosis, prevention, and treatment of diseases and problems specific to the aged.
老年牙医学牙科学分支，专门研究老年人牙病和问题的诊断、预防和治疗
They have begun to do the prevention of crime.
他们已经开始防止犯罪行为。
