In medicine, patient adherence describes the degree to which a person correctly follows medical advice. Most commonly, it refers to medication or drug compliance, but it can also apply to other situations such as medical device use, self care, self-directed exercises, therapy sessions, or medical follow-up visits. Patient compliance and patient adherence may be used interchangeably but adherence emphasizes the role of the patient in decision-making and factors that influence the ability to follow instructions. Concordance is the process by which a patient and clinician make decisions together about treatment. Differences in terminology reflect regional variation, deliberate distinctions, and the preferences of various groups and organizations.