As our knowledge of dental caries and periodontal diseases has increased, our perspective has changed from viewing these diseases as ubiquitous to one which sees a variety of risk profiles in a population. Now, from a perspective of assigning risk, caries and periodontitis can be thought to be more like some of our common medical conditions, i.e., certain people or subgroups of the population are at higher risk than others and that prevention and intervention involve a combination of personal behaviors and professional practices. Research into risk assessment, however, is often hampered by confusing and ambiguous use of terminology. This commentary proposes some specific definitions for terms used in risk assessment in dentistry. These terms include risk factor, risk indicator, demographic risk factor, risk predictor (risk marker), prognostic factor, risk model, and prediction model.