condition: a general term for diseases, lesions and disorders; often excludes mental health, where disorder is preferred (e.g. Diagnostic and statistical manual of mental disorders)
disease: a condition that impairs the normal function of a person, plant or animal. Diseases can be communicable (spread to a person from an animal, the environment or another person – e.g. measles, HIV, malaria, influenza) or noncommunicable (caused by environmental or genetic factors – e.g. cardiovascular diseases, cancer, diabetes, chronic respiratory diseases)
disorder: a synonym for disease (i.e. a functional abnormality), used for noninfectious conditions such as physical, metabolic or mental conditions; in mental health, mental disorder is preferred to mental illness
illness (sickness): a synonym for disease but often used to indicate the person’s experience of a disease (i.e. a person can have a disease without being ill or sick)
syndrome: the occurrence of several associated medical signs, symptoms or other characteristics (e.g. Down syndrome)
See also Disease names