A clinical terminology is a structured list of terms for use in clinical practice. These terms describe the care and treatment of patients and cover areas like diseases, operations, treatments, drugs, and healthcare administration.

Medical classification, or medical coding, is the process of transforming descriptions of medical diagnoses and procedures into universal medical code numbers. Diagnosis codes are used to track diseases, whether they are everyday diseases such as diabetes mellitus and heart disease, to contagious diseases such as norovirus, the flu, and athlete's foot. These diagnosis and procedure codes are also used by health insurance companies and workers' compensation carriers.

Medical classification systems are used for a variety of applications in medicine and medical informatics

    * statistical analysis of diseases and therapeutic actions
    * reimbursement, e.g. based on DRGs
    * knowledge-based and decision support systems
    * direct surveillance of epidemic or pandemic outbreaks