Criminology is the study of nonlegal aspects of criminal behavior. It is a sociological field, focused on causes, prevention, and corrective actions as related to criminal behavior. The major subgroups of criminology are biological, classical, criminalistics, penology, psychological, and sociological. The field of study itself is used to inform alterations to the criminal justice system (penology specifically focuses on prisons and prison systems), police reform efforts, assessing criminal behavior in order to prevent its recurrence based on specific factors, and assessing criminal behavior in order to better understand the intent behind it and determine what the resulting punishment ought to be.